Reword, fix typo
Remove Swap() methods as there's std::swap for this
Add Point and Rect setters

While here, fix Rect::GetX2 and Rect::GetY2 off-by-one errors
Add Point and Rect comparison operators
Define default ctors/assignments in source files to avoid using objects of incomplete type in them
Properly handle self-assignment
Add Point and Rect tests
Fix Rect::FromCenter and add test for it
Improve testing framework, add stub for GUI tests
Make travis run tests
Implement Renderer::ReadPixels
Add partial GUI test