Add HideHelp flag in App and Command
Hide "Options" sections in help, if no flags are defined
Fix Subcommand help text
Fix tests
Add Args.Swap command for swapping arguments

The usecase:
my-cli user <USERID> set <FIELD> <VALUE>

Being able to swap <USERID> with set argument, we can have nested subcommands while preserving all variable arguments along the way.
Add App.RunAndExitOnError shortcut
Run `go vet` as part of Travis build
Merge pull request #116 from modcloth/add-go-vet-to-travis-build

Run `go vet` as part of Travis build
Merge pull request #115 from AudriusButkevicius/hidehelp

Make help command optional
Merge pull request #114 from AudriusButkevicius/shortcut

Add App.RunAndExitOnError shortcut
Merge pull request #112 from AudriusButkevicius/swap

Add Args.Swap command for swapping arguments
Add App and Command argument count checking