Use released versions in dev-requirements
Use released versions in dev-requirements

This commit replaces the dev dependencies declared as repositories by
the latest associated release of betamax and betamax_matchers.

icio/github3.py,degustaf/github3.py,balloob/github3.py,sigmavirus24/github3.py,itsmemattchung/github3.py,ueg1990/github3.py,krxsky/github3.py,jim-minter/github3.py,agamdua/github3.py,christophelec/github3.py,h4ck3rm1k3/github3.py