Adding built-in version command, fixes #11

[rorticus]

Adding version command. This command is built into cli core and will show the version of all the registered commands.

Usage:

$ dojo version

Example output with no commands,

There are no registered commands available.

You are currently running dojo-cli 2.0.0-pre

Example output with commands,

The currently installed groups are:

create (dojo-cli-create-app) 2.0.0-alpha.2

You are currently running dojo-cli 2.0.0-pre

What the help looks like,

dojo help

Usage: dojo <group> <command> [options]

Hey there, here are all the things you can do with dojo-cli:

Commands:
  create   Scaffolds a new command
  version  List versions of registered commands

Options:
  -h, --help     Show help                                             [boolean]
  -v, --version  Show version number                                   [boolean]

For more information on any of these commands just run them with '-h'.

e.g. 'dojo run -h' will give you the help for the 'run' group of commands.

[codecov-io]

Current coverage is 99.38% (diff: 100%)

Merging #64 into master will increase coverage by 0.18%

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  Methods           0          0          
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  Branches          9         13     +4   
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+ Hits            125        162    +37   
  Misses            1          1          
  Partials          0          0          

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[agubler]

Can we add some general JSDoc, especially for exported interfaces / function / types?

[rorticus]

@agubler says,

Can we add some general JSDoc, especially for exported interfaces / function / types?

Done!