Run `capify .` with `bundle exec`

For us with multiple versions of Capistrano installed, `capify!` fails
when using Capistrano 3. Replacing `capify!` with the contents of
https://github.com/rails/rails/blob/master/railties/lib/rails/generators
/actions.rb#L208 + `bundle exec`
Removes extra whitespace!
Merge pull request #23 from smashingboxes/bundle_capify

Bundle capify