Fixes for Mac App Bundle and OpenGL on macOS

Modifications to pull the data from Application Support in macOS in order to facilitate distribution as a n App Bundle.

Also incorporated code from this unmerged PR to fix issues with OpenGL
Interrupt#409

Changed SDL2_Mixer version check

For some reason it's not detecting versions > 2.0.4 even though it should

Updated build script for dual versions

Merge pull request Interrupt#349 from mrikola/fix-travis-deployment

Fix travis deployment

Merge pull request Interrupt#346 from icosahedral-dragon/fix-cursor-a…

…nd-damage-crashes

Fix cursor and damage crashes

Merge pull request Interrupt#332 from mrikola/update-readme

Bring readme files up to date

Merge pull request Interrupt#303 from mrikola/focus-mouse-on-startup

Improve mouse focus logic

Merge pull request Interrupt#300 from mrikola/add-no-default-path-dir…

…ectives

Add NO_DEFAULT_PATH to further force local SDL libraries

Merge pull request Interrupt#274 from mrikola/remove-findsdl

Remove FindSDL2 scripts in favor of using our own

Merge pull request Interrupt#268 from donnierussellii/gamma-slider-re…

…nder

Render 3d view when using gamma slider