solve bookstrap-dependency-bug

[eins78]

right now the default template (bookstrap) ist not really usable.
trivial solution is to manually clone the repo, add to project and fill it in papermill.json.

the actual solution involves several enhancements:

• use npm as a library to enable installing deps from a papermill.json (use npm as a library #18)
• same with bower, but reps would be in bowerDependencies (?) (use bower as a library #19)
• to make it usable, use grunt-init internally for mill new (use grunt-init as a library #20)