Removed libpng dependency and added stb_image_write to the project.
Removed libpng from README and added stb_write_image.
Replace libPNG with stb_image_write.

See issue #18.
Fixed directory structure.
Fixed directory structure.

See issue #17.
Got colour intensities closer to POVRay's.
Fix light intensities so that they are closer to POVRay's.

See issue #14.
Fixed some inaccuracies in transparency.
Fixed noise in mount scene.
Added post-processing (normalization and gamma correction).
Fixed brigthness problem, wasn't multiplying diffuse colour with the diffuse co-efficient.
Fix brightness issue.
Merge branch 'develop'