Bump version to v0.1.6

Update variable/function docs.
More document for in-module completion
Avoid to call length when putting text property
Call company-ghc sub commands via company-ghc
Implement hoogle search completion command
Document for hoogle search completion, bump to v0.1.7
Add unit test for company-ghc--hoogle-candidates

By using dummy hoogle command.
Fix order of hoogle search results and regexp