Move ArgumentParserImpl#getFormatWidth() to ArgumentParsers

ArgumentParsers#getFormatWidth() is public static method and application
code can use it to get column width to format its own text output.
ArgumentParserImpl#FORMAT_WIDTH was also moved to ArgumentParsers and
renamed as DEFAULT_FORMAT_WIDTH.
Added shortcut method to parse arguments and handle errors.
Don't print trailing white spaces when no argument help is provided
Add "hidden" argument support

If Argument#help(FeatureControl) is invoked with parameter
Arguments.SUPPRESS, the help entry of that option will not be
displayed.
check file syntax fire, only then check file system
Document usage of Argument#help(Arguments.SUPPRESS)
Close BufferedReader in ArgumentParserImpl#extendArgs()
Add test case for fromFilePrefixChars and Subparsers
Don't show suppressed option in mutex group error message
Upgrade to fluido skin 1.3.0
site: Fixed duplicate help anchor
Rename README.txt as README.rst
Change issue tracker to github
Update license year
Add note about trailing empty lines or white spaces in argument file
Bump up version to 0.3.0-SNAPSHOT
Add additional help message for unrecognized args from file

If trailing empty lines or white spaces exist in argument file
accidentally, the error message is typically only "unrecognized
arguments" and it may be hard to notice that the problem is in a
file. To help the user in this situation, if the unrecognized
argument was coming from a file, add additional help message to
the exception message to alert user that the problem may exist in
argument file. This change also quotes unrecognized arguments in
exception message.
Update unrecognized arguments error from argument file

Surround fromFilePrefixChars with square brackets because they
can be multiple characters.
Add public static ArgumentParsers.DEFAULT_PREFIX_CHARS

It is the default value of prefixChars which can be passed to
ArgumentParsers.newArgumentParser().
Format error message according to column width