Updated the library to follow good practices on library organization, added compatibility with browser (#14)

* Updated the library to follow good practices on library organization

* Updated imports to comply with https://dart-lang.github.io/linter/lints/avoid_relative_lib_imports.html

* Fix format

Author: marcgraub

lib/logger.dart

@@ -1,21 +1,19 @@
 /// Small, easy to use and extensible logger which prints beautiful logs.
 library logger;
 
-import 'dart:collection';
-import 'dart:convert';
-import 'dart:io';
+export 'src/ansi_color.dart';
 
-import 'src/ansi_color.dart';
+export 'src/filters/debug_filter.dart';
+export 'src/filters/production_filter.dart';
+export 'src/outputs/console_output.dart';
+export 'src/outputs/memory_output.dart';
+export 'src/printers/pretty_printer.dart';
+export 'src/printers/simple_printer.dart';
 
-part 'src/filters/debug_filter.dart';
-part 'src/filters/production_filter.dart';
-part 'src/outputs/console_output.dart';
-part 'src/outputs/file_output.dart';
-part 'src/outputs/memory_output.dart';
-part 'src/printers/pretty_printer.dart';
-part 'src/printers/simple_printer.dart';
+export 'src/log_output.dart'
+    if (dart.library.io) 'src/outputs/file_output.dart';
 
-part 'src/log_filter.dart';
-part 'src/log_output.dart';
-part 'src/log_printer.dart';
-part 'src/logger.dart';
+export 'src/log_filter.dart';
+export 'src/log_output.dart';
+export 'src/log_printer.dart';
+export 'src/logger.dart';

lib/src/filters/debug_filter.dart

@@ -1,4 +1,5 @@
-part of logger;
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_filter.dart';
 
 /// Default implementation of [LogFilter].
 ///

lib/src/filters/production_filter.dart

@@ -1,4 +1,5 @@
-part of logger;
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_filter.dart';
 
 /// Prints all logs with `level >= Logger.level` even in production.
 class ProductionFilter extends LogFilter {

lib/src/log_filter.dart

@@ -1,4 +1,4 @@
-part of logger;
+import 'package:logger/src/logger.dart';
 
 /// An abstract filter of log messages.
 ///

lib/src/log_output.dart

@@ -1,4 +1,4 @@
-part of logger;
+import 'package:logger/src/logger.dart';
 
 /// Log output receives a [OutputEvent] from [LogPrinter] and sends it to the
 /// desired destination.

lib/src/log_printer.dart

@@ -1,4 +1,4 @@
-part of logger;
+import 'package:logger/src/logger.dart';
 
 /// An abstract handler of log events.
 ///
@@ -8,7 +8,7 @@ part of logger;
 ///
 /// You can implement a `LogPrinter` from scratch or extend [PrettyPrinter].
 abstract class LogPrinter {
-  List<String> _buffer;
+  List<String> buffer;
 
   void init() {}
 
@@ -20,6 +20,6 @@ abstract class LogPrinter {
 
   /// Sends a line to the [LogOutput].
   void println(String line) {
-    _buffer.add(line);
+    buffer.add(line);
   }
 }

lib/src/logger.dart

@@ -1,4 +1,9 @@
-part of logger;
+import 'package:logger/src/filters/debug_filter.dart';
+import 'package:logger/src/printers/pretty_printer.dart';
+import 'package:logger/src/outputs/console_output.dart';
+import 'package:logger/src/log_filter.dart';
+import 'package:logger/src/log_printer.dart';
+import 'package:logger/src/log_output.dart';
 
 /// [Level]s to control logging output. Logging can be enabled to include all
 /// levels above certain [Level].
@@ -61,8 +66,8 @@ class Logger {
         _printer = printer ?? PrettyPrinter(),
         _output = output ?? ConsoleOutput() {
     _filter.init();
+    _printer.buffer = _outputBuffer;
     _filter.level = level ?? Logger.level;
-    _printer._buffer = _outputBuffer;
     _printer.init();
     _output.init();
   }
@@ -121,7 +126,7 @@ class Logger {
         }
         _output.output(outputEvent);
         _outputBuffer = [];
-        _printer._buffer = _outputBuffer;
+        _printer.buffer = _outputBuffer;
       }
     }
   }
@@ -132,7 +137,7 @@ class Logger {
     _outputBuffer = null;
     _filter.destroy();
     _printer.destroy();
-    _printer._buffer = null;
+    _printer.buffer = null;
     _output.destroy();
   }
 

lib/src/outputs/console_output.dart

@@ -1,4 +1,5 @@
-part of logger;
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_output.dart';
 
 /// Default implementation of [LogOutput].
 ///

lib/src/outputs/file_output.dart

@@ -1,4 +1,8 @@
-part of logger;
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_output.dart';
 
 /// Writes the log output to a file.
 class FileOutput extends LogOutput {

lib/src/outputs/memory_output.dart

@@ -1,4 +1,7 @@
-part of logger;
+import 'dart:collection';
+
+import 'package:logger/src/logger.dart';
+import 'package:logger/src/log_output.dart';
 
 /// Buffers [OutputEvent]s.
 class MemoryOutput extends LogOutput {