Improve OpenGL clipping when using emulated SDL2 independent scaling
travis-ci: Enable email notifications
Image: Introduce ::load_memory
Convert ::LoadTexture, ::GenerateTexture to use nomlib's abstraction
Renderer: Introduce ::set_scale.

* Renderer: Rename ::scale_factor to ::scale.
GradientTest: Use set_scale in Margins test
Introduce Point2(int), Size2(int) ctors

* MathTest: Add tests for these new ctors