audio: clamp overflowing values
Merge branch 'master' into audio
jobmanager: add jobmanager and integrate it into engine
jobmanager: fix header guard typo
jobmanager: add this-> to members and add comments
audio: rename ResourceLoader to InMemoryLoader
audio: basic dynamic audio loading is working
audio: add comments, small fixes
Convert `doc/` to markdown
Merge branch 'audio' into jobmanager

This brings background loading for audio files.

Conflicts:
	src/CMakeLists.txt
	src/audio/audio_manager.cpp
	src/audio/audio_manager.h
	src/audio/resource_loader.cpp
	src/audio/resource_loader.h
	src/engine/audio/in_memory_loader.cpp
	src/engine/audio/resource_loader.cpp
	src/engine/engine.cpp
	src/engine/engine.h
	src/engine/init.cpp
testing: using dynamic background audio loading
util/fps: properly initialize variables for fps counter
engine: removed unique_ptr for the global engine instance

this fixes the segfault in ftgl/freetype.
testing: fixed memleaks in generated filenames

the free could be skipped when the loop is continued.
ci: install gcc-4.8 for stdlib even when building with clang
ci: removed friendly reminders for travis staff
ci: use gcc-4.9 on travis
ci: use gcc package name instead of g++
ci: back to gcc 4.8 as travis is still on precise

the ubuntu toolchain ppa doesn't have a gcc-4.9 for precise.
seriously travis, please update your machines.
make: no more -Werror in release build