Added regression test in tests/advection_2d_square that checks sum of t and q at two gauges
Added tests/advection_2d_annulus
Added tests/acoustics_2d_radial
Added regression_tests.py to examples/advection_2d_square:  compares to gallery version...
See comments in file.
Also fixed bugs in clawpack/clawutil/src/python/clawutil/imagediff.py
on branch regression_imagediff
Added tests/run_tests.py and improved advection_2d_square/regression_tests.py
modified tests/advection_2d_square to save and read regression results rather than hardwiring into script
Changed other tests to read in archived data
added tests/Makefile and more to README
improved comments
fixed examples/acoustics_2d_radial to add .m files from @donnaaboise PR #65 and fix 1drad subdirectory to properly use new classic code
fixed README file
fixed README file again
Merge pull request #72 from rjleveque/radial_acoustics

Radial acoustics
Merge pull request #73 from mjberger/master

missing maux and dimension statement, also adds some name changes.
3d uses modules, new output formats
acoustics_3d_interface example with setrun.py and matlab plotting .m files
Merge branch 'master' into regression

PR #69 is out of date relative to more recent changes -- merging those in to
check that regression tests still work.

* master:
  changed to use dt_max in setrun.py to avoid huge cfl numbers when vt=0
  changed name of unused variable dtv2 -> dt_max. Add line to use it in tick - default in setrunn is 1e98 so shouldn't change anything unless actually set it in setrun.py:
  added dimension statement for aux - safer this way
  tstart var in conck should have been changed when variable replaced by either tstart_thisrun or t0
  missing maux and dimension statement
  fixed README file again
  fixed README file
  fixed examples/acoustics_2d_radial to add .m files from @donnaaboise PR #65 and fix 1drad subdirectory to properly use new classic code
  missing aux argument in qinit
  change README.txt to .rst. Most files only have titles, little description yet.
added example euler_3r_radial. minor code tweaks
Improved regression tests to make it easier to adapt to new problems
shockbubble example converted