amp version option

[neha-viswanathan]

Ref #458

Added command to display amp version. The following commands display the version of amp.

amp version
amp -V
amp --version

Output:

amp (cli version: v0.4.0-dev, build: 55bfccb1)
Usage:	amp COMMAND

Appcelerator Microservice Platform.

Options:
      --config string   Config file (default is $HOME/.amp.yaml)
  -h, --help            help for amp
      --server string   Server address
  -v, --verbose         Verbose output
  -V, --version         Version number

Commands:
  config      Display the current configuration
  info        Display amp version and server information
  login       Login via github
  logs        Fetch log entries matching provided criteria. If provided, SERVICE can be a partial or full service id or service name.
  registry    Registry operations
  service     Manage services
  stack       Stack operations
  stats       Display resource usage statistics
  topic       topic operations
  version     Display the version number of amp

Run 'amp COMMAND --help' for more information on a command.