Add basic 1d point-wise Riemann solvers

Includes the initial version of the wrapper harness for point-wise Riemann
solver and an example of the scalar advection and acoustics point-wise Riemann
solver implementations.
Add setup and build support for PyClaw
Fix point-wise advection bug
Implement rename of ptwise sovlers
Add 2d point-wise solver support

Includes PyClaw build support and an acoustics example Riemann solver.
Merge pull request #91 from mandli/ptwise

[WIP] Adds Point-Wise Versions of the Riemann Solvers