Merge pull request #2 from dpla/gemify

Prepare a 4.0.0.0.pre.1 release
Adjust ActiveTriples & linked_vocabs dependencies

Loosen pessimistic dependency on linked_vocabs to accept pre-1.0
versions. Push ActiveTriples to ~>0.3.0.
Move shared factories into lib

This allows `require 'dpla/map/factories'` to use this gem's factories
in another gem.