2.2 alpha 1 version release

Merge pull request maxirobaina#96 from toshiroakio/patch-1

Update expressions.py fix for python3

Prepared to new release 1.10

Prepared for 1.9.0 release

Bumped version for 1.9.0 final
Dropped support for Python 2.6, 3.2, 3.3
Update changelog

[1.8.x] Update changelog

Fixed maxirobaina#69 - DecimalField value is not converted correctly

Update README

Bump version to 1.7.1

Bumped version for 1.7.0 release.

Bump version to 1.6.4