Merge pull request #42 from gradylemoine/acoustic-1d-setplot

Adding setplot mimicking book Figure 9.5
changed to read dt_variable as logical in 1d and 2d
Merge pull request #44 from rjleveque/dt_variable

change dt_variable to a logical variable in fortran codes to match data.py
Switching to 3D-style interpretation of dt_variable