Streamlined GLSL shaders

Stripped down the GLSL shaders to the minimum needed. Separate texture
shader for background and shader for waves.
Add builder pattern for OtoVisualizer

Add a builder for creating new instance of OtoVisualizer as to make it
easier to customize.
Basic texturing mapping

Very basic texture mapping on background node.
Update README

Quick update to the READ.md file to reflect changes from last merged
branch.