Merge pull request #745 from bvssvni/master

Point img_hash to PistonDevelopers fork
Merge pull request #746 from bvssvni/master

Reexported Conrod
Merge pull request #747 from bvssvni/master

Reexported dsp-chain
Merge pull request #750 from bvssvni/master

Added portaudio to Travis CI
Upgraded to latest piston-graphics