setup: pin SQLAlchemy-Continuum to < 1.3.5

this version introduces a bug when unit testing the application.
See https://github.com/kvesteri/sqlalchemy-continuum/issues/188 for
details.

use http protocol instead of https when mocking with httpretty. Test
fail beginning with version 0.9.5 of httpretty
6 jobs for remove-versioning-dependency in 24 minutes and 52 seconds (queued for 2 seconds)