support for getting alternate name flag values from yaml/toml/json

[pysqz]

fix issue #711. please check~

[mdbraber]

Thanks for creating this patch, hope this gets merged soon! For those who want to use this now:

go get gopkg.in/urfave/cli.1
cd $GOPATH/src/gopkg.in/urfave/cli.1
git remote add upstream https://github.com/pysqz/cli-1.git
git fetch upstream
git checkout remotes/upstream/master

[mdbraber]

It seems that this fix doesn't work yet with NewStringSliceFlag. Any ideas what could be changed?

[pysqz]

Repush a patch #792. It can fix this bug with StringSliceFlag and IntSliceFlag. Please review again~ @mdbraber