Add failOnExtraFlags option to Args.parse()

If set to false, parse will ignore any extra flags in the args array and simply
return them with the other unconsumed arguments.
Merge pull request #7 from andrewpurcell/master

Add failOnExtraFlags option to Args.parse()
Revert "Add an option to allow unrecognized options"

This reverts commit c79707a4ab965ed62cefc3880e00fef082ca4b86.
Merge branch 'master' of github.com:spullara/cli-parser