Burgers convergence (#168)

I fix the Burgers solver so that it is completely based on incompressible. Also changed the visualization to plot u and v separately.

Moved the riemann and upwind functions to burgers_interface to avoid circular imports in a future pr.

I'll do some cleaning for incompressible later.

Author: zhichen3

docs/source/burgers.png

@@ -9,10 +9,19 @@ pyro.burgers.problems package
 Submodules
 ----------
 
-pyro.burgers.problems.smooth module
+pyro.burgers.problems.test module
 -------------------------------------
 
-.. automodule:: pyro.burgers.problems.smooth
+.. automodule:: pyro.burgers.problems.test
+   :members:
+   :undoc-members:
+   :show-inheritance:
+
+
+pyro.burgers.problems.converge module
+-------------------------------------
+
+.. automodule:: pyro.burgers.problems.converge
    :members:
    :undoc-members:
    :show-inheritance:

docs/source/pyro.burgers.problems.rst

@@ -17,10 +17,10 @@ Subpackages
 Submodules
 ----------
 
-pyro.burgers.advective\_fluxes module
+pyro.burgers.burgers\_interface module
 ---------------------------------------
 
-.. automodule:: pyro.burgers.advective_fluxes
+.. automodule:: pyro.burgers.burgers_interface
    :members:
    :undoc-members:
    :show-inheritance: