Switchin from GTest to Catch for testing
Fix a few CMake things
Adding threading test, and fixing a tiny CMake issue
Merge branch 'master' into catch
Use the correct STL atomic type
Fixing wording, and adding more threading tests
Threaded test now compiles and runs on Travis
Update Doxyfile to Doxygen 1.8.7
Adding entity tests for advanced component usage
Starting work on removing freeze reasons

This should help make the Entity System more durable
Merge branch 'freeze-cleanup' into catch
Working on component and entity tests
A few small fixes
Working on removing more reasons for the Entity System to freeze

This will probably break if requests are made or removed at the same time as components change in an entity though
Merge branch 'catch'