allow customization of test templates

[macrozone]

fixes https://github.com/mantrajs/mantra-cli/issues/87

few notes:

test-templates can be configured with:

 - name: 'component'
    test: true
    text: |
      import .....

I also thought about using `name: 'component-test', but i thought options would be better, as we could easily add more options (e.g. for variants like class instead of arrow function in components)

sidenote:

currently there are options for astronomy and collection2 scheme. I would deprecated these options in favor of better customization.

[macrozone]

I released an rc.4 that fixes this issue.

[sungwoncho]

Merged. 👍