Update step3.f90

Update to fix bug related to capacity function for transverse_waves = 21 and 22
dtdx, dtdy, and dtdz need to be divided by the capacity function when passed into flux3()
Update flux3.f90

Fixed bug for transverse_waves==21 and 22 where dtdz and dtdy need to be divided by the capacity function.  These are passed from step3.f90.  The variable names have been changed to reflect this change.
Test script for the newly added 3D Euler Equations using F-Wave

Adding a hot sphere rising in a stabilized equilibrium atmosphere for the 3D Euler equations in Cartesian coordinates.  Riemann solver added with PR: https://github.com/clawpack/riemann/pull/85
Test script for the newly added 3D Euler Equations using F-Wave in Spherical Coordinates

Adding a hot sphere rising in a stabilized equilibrium atmosphere for the 3D Euler equations in Earth centered spherical coordinates.  Riemann solver added with PR: clawpack/riemann#85
Merge branch 'master' of https://github.com/weslowrie/pyclaw