Added test for gauges, fixed a bug in grid.add_gauges, removed the use of solver.set_riemann_solver function and Modified parameter 'g' to be 'grav' for consistency.
Change the location
of attributes gauge_data and keep_gauges from Grid to State classes
Modifications to code for storing gauges in memory and modifications related to using the (reltol) for
the 2D psystem test
separating the removal of set_riemann_solver uses from other changes related to gauges
change in the error message generated when running nosetests that corresponds to the suggested
minor style modification
Merge pull request #214 from amal-ghamdi/fix_and_test_gauges

Fix and test gauges