add design docs on db creation, use Pathname

Pathname makes dealing with files easier than String.

Tapicero will look for design documents in design directory in the tapicero path for now.
add design docs to be included in each user database

Also strip the .json extention because soledad does not expect it
proceed if design docs are already there

We'll add a flag to overwrite designs and / or security later. For now just make sure this does not crash tapicero.
Version 0.3.0: include design docs on created databases
Merge pull request #6 from azul/deploy-design-docs

Deploy design docs