Issue64 Remove a byte order mark if strSource begins with BOM.

Fix for issue #64 "file encoding problem"
Steps to reproduce with gosu-0.10.2
1. Create test hello.gsp file with UTF-8 and BOM from Terminal application on Mac OS X
$ echo '\ufeffprint("hello!")' | native2ascii -encoding UTF-8 -reverse > hello.gsp
2. Run test file on Mac OS X or Windows
// expected result: Script displays output without exception.
$ ./bin/gosu -f hello.gsp 
hello!
// actual result: Exception is displayed as 	
$ ./bin/gosu -f hello.gsp 
gw.lang.parser.exceptions.ParseResultsException: user.gosu-0.10.2.hello

Errors: 

No function defined for ﻿print. [line:3 col:1] in
line 2: 
Line Number: 1  Column: 1


	at gw.internal.gosu.parser.ParserBase.verifyParsedElement(ParserBase.java:285)
	at gw.internal.gosu.parser.ParserBase.verifyParsedElement(ParserBase.java:256)
	at gw.internal.gosu.parser.GosuClassParser.parseDefinitions(GosuClassParser.java:458)
	at gw.internal.gosu.parser.GosuClass.compileDefinitionsIfNeeded(GosuClass.java:1482)
	at gw.internal.gosu.parser.GosuClass.compileDefinitionsIfNeeded(GosuClass.java:1423)
	at gw.internal.gosu.parser.GosuClass.isValid(GosuClass.java:817)
	at gw.internal.gosu.parser.GosuProgram_Proxy.isValid(gw.internal.gosu.parser.GosuProgram_Proxy:2)
	at gw.internal.gosu.parser.GosuProgramParser.parseExpressionOrProgram(GosuProgramParser.java:188)
	at gw.lang.Gosu$ExecuteMode.runWithFile(Gosu.java:766)
	at gw.lang.Gosu$ExecuteMode.run(Gosu.java:723)
	at gw.lang.Gosu.start(Gosu.java:123)
	at gw.lang.launch.impl.GosuLauncher.run(GosuLauncher.java:143)
	at gw.lang.launch.impl.GosuLauncher.main(GosuLauncher.java:63)