First pass at JSONParser system

The system knows how to load resources given a set format:
// "resources": {
//   "type" : {
//     "name": {
//       "prop_name_string": "prop_value",
//       "prop_name_int": 1,
//       "prop_name_double": 1.0f,
//       "prop_name_bool": False
//     }
//   }
// }

FindRapidJSON was pulled from https://raw.githubusercontent.com/jdduke/three_cpp/master/cmake/FindRapidJSON.cmake
Style changes on ResourceSystem.h/cpp

JSONParser now stores a map of serializable types.
This type is based on the top level object in the JSON file.
Attempt to fix travis
One more attempt
Fixed some style issues that occurred

Moved ResourceSystem into the system namespace.
Style fixes

Still need to rename some files to use lower-case names.
Made the tests source files less error prone

This is done by explicitly including the source files
in the CMakeLists file in tests.

Also added a fix for RapidJSON for OS X.
Merge branch 'feature-json-loader' into develop