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
Remove all the uses of set_riemann_solver function
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
Merge pull request #213 from amal-ghamdi/issue_184_cont

Remove all the uses of set_riemann_solver function
change from absolute to relative tolerance in testing acoustics 2D: issue #209
remove two unnecessary lines
Merge pull request #215 from amal-ghamdi/issue_209

Issue 209: replace the use of absolute error with relative error in testing homogenous acoustics 2D
add a flag to call before_step before each RK stage
Merge pull request #218 from amal-ghamdi/add_flag_sharpclaw_solver

add a flag "call_before_step_each_stage" to call before_step before each RK stage
Use indices in testing whether on
a boundary. This is done to avoid using the upper and lower coordinate extents
in this check as floats equality comparison is not safe."
initial hacking to add flags for boundaries
add flags to the grid and dimension
objects to indicate whether the grid is on boundary
use on_lower_boundaries and on_upper_boundaries grid
flags in the methods apply_q_bcs and apply_aux_bcs instead of
making indices comparison
correct spelling error
Merge pull request #220 from amal-ghamdi/add_bc_flags

solution for issue #154, adding boundary flags