cobra's generated 'help' description is not capitalized.

[Dimrok]

Just a small detail but the generated help for <command_name>, unlike the other help messages, is not capitalized.

How to reproduce

$ docker-app init --help
[...]
Flags:
  -c, --compose-file string      Initial Compose file (optional)
  -d, --description string       Initial description (optional)
  -h, --help                     help for init
  -m, --maintainer stringArray   Maintainer (name:email) (optional)
  -s, --single-file              Create a single-file application

Version

$ docker-app version
Version:      0.1.0-162-g9b311d2
Git commit:   9b311d2
Build time:   2018-06-07T12:36:50.253486313+00:00
OS/Arch:      linux/amd64
Experimental: off
Renderers:    none

[vdemeester]

In docker/cli we override the description of help (see https://github.com/docker/cli/blob/09115e37501d544b286c091522c437eee6c40a28/cli/cobra.go#L27), we do the same here

[Dimrok]

I'll fix that.