Merge branch 'release/0.4.6' into develop
PyContracts needs PyParsing but PyParsing >= 2.0.0 doesn't work with python 2 so we force it to use the old version '< 2.0.0'.
0.4.7:
    PyContracts needs PyParsing but PyParsing >= 2.0.0 doesn't work with python 2 so we force it to use the old version '< 2.0.0'.
Merge branch 'release/0.4.7'