[padrino-gen] Adjust to RSpec3, and little fix

to the rake task:
* remove the formatting option
* add description to dynamic tasks
* using 'each_with_object' instead of 'inject'

to the templates:
* adjust to RSpec3 syntax
* set to be pending in the initial state
Restore controller default test case in rspec template
Merge pull request #1705 from tyabe/fix_padrino-gen

[padrino-gen] Adjust to RSpec3, and little fix