Remove simplejson

[pchien]

All the python versions supported (2.7, 3.4+) have the json module by default. The simplejson version pinned here is very old and some other libraries use simplejson over json by default (probably for old compatibility reasons).

I think it's preferable to remove it, but if you want to keep simplejson around it should at least be a more recent version for better compatibility with other libraries.

[coveralls]

Coverage decreased (-0.04%) to 48.262% when pulling a2264d2 on mobilizeamerica:master into 7d6e820 on martyzz1:master.