Improve help message when using "plonecli -l"

[idgserpro]

• Plone CLI version:

0.2.0

• Python version:

2.7.9

• Operating System:

Description

Improve help.

What I Did

plonecli -l                                                                                                                                                                     [17:21:31]
Available mr.bob templates:
 - buildout
 - addon
  - vocabulary
  - theme
  - behavior
  - content_type
 - theme_package

And then:

plonecli create addon                                                                                                                                                           [17:21:55]
Usage: plonecli create [OPTIONS] TEMPLATE NAME
Try "plonecli create -h" for help.

Error: Missing argument "name".

I suggest adding the last message plonecli create addon src/collective.todo available at the official docs https://github.com/plone/plonecli#creating-a-plone-add-on. It would be nice to solve #28 before this issue.