Version bump to 4.2.7 and updating CHANGES.txt
test python 2.6
Merge branch 'stage'
autopep8
make OrderedDict accessible to python 2.6
cleanup install requirements
dont support python 2.6
setup fail on < 7, not <=
correct and warn if fcst < 0
make sure polynomial cost coefs and fuelcosts are floats
add wind_capacity_factor option