Fix travis's pypi release trigger

Merge pull request MongoEngine#1737 from CalgaryMichael/remove-pushall

Removing the usage of the '$pushAll' operator

Bump version to 0.15.0

v0.14.3 version bump

remove {nospam} from author_email & maintainer_email (PyPI doesnt val…

…idate those anymore)

v0.14.1 version bump + updated changelog

more docs tweaks [ci skip]

bump version to v0.13.0 and fill in the changelog and the upgrade docs

update the changelog and bump the version to v0.12.0

version bump