Update the duct_flow test case with code implementing the analytical solution.
Fix the initial velocity profile in the channel flow example.
Update the geometry of the channel flow.
Add sanity checks and make it easy to switch BC in the channel flow
example.
Update installation docs.

Updates:
 - Ubuntu installation instructions
 - list of required dependencies

Adds:
 - generic installation instructions for Linux
Add the VisConfig wrapper object.
Make the visualizer UI more responsive.
Add suport for data bucketization in the VisMixIn class.
Explicitly initialize font module in pygame visualization.