Drop results.dart (#119)

I can't find any usages. Since nothign in this library consumes or
produces instances of these classes it's likely that any code has a
dependency on them.

Author: natebosch

CHANGELOG.md

@@ -5,6 +5,7 @@
   * Move cli_util to dev_dependencies
   * Avoid some deprecated analyzer apis
   * Syntax tweaks
+  * Drop results.dart which had no usages
 
 ## 0.5.2
 

lib/source_gen.dart

@@ -1,6 +1,5 @@
 library source_gen;
 
 export 'src/builder.dart';
-export 'src/results.dart';
 export 'src/generator.dart';
 export 'src/generator_for_annotation.dart';