Add tests and docs for parse_file

Author: tkelman

README.md

@@ -292,6 +292,9 @@ set_attributes(e, key1="val1", key2="val2", ...)
 
 ```julia
 xdoc = parse_file(filename)  # parse an XML file
+xdoc = parse_file(filename,  # parse an XML file with a specified encoding and parser options,
+         encoding, options)  # see http://xmlsoft.org/html/libxml-parser.html#xmlReadFile
+                             # and http://xmlsoft.org/html/libxml-parser.html#xmlParserOption
 xdoc = parse_string(str)     # parse an XML doc from a string
 save_file(xdoc, filename)    # save xdoc to an XML file
 

test/parse.jl

@@ -21,7 +21,9 @@ docstr = """
 </bookstore>
 """
 
-xdoc = parse_string(docstr)
+for xdoc = (parse_string(docstr),
+            parse_file(joinpath(dirname(@__FILE__), "ex1.xml")),
+            parse_file(joinpath(dirname(@__FILE__), "ex1.xml"), C_NULL, 64)) # 64 == XML_PARSE_NOWARNING
 
 @test version(xdoc) == "1.0"
 @test encoding(xdoc) == "UTF-8"
@@ -152,3 +154,4 @@ cz = find_element(xb1, "abc")
 @test is(cz, nothing)
 
 free(xdoc)
+end