Fixed bug in pressure for isentropic vortex problem as pointed out by Kevin Schaal. See http://www.cfd-online.com/Wiki/2-D_vortex_in_isentropic_flow
Merge pull request #15 from juanpablogallego/master

Correct positivity limiter check loop for average values under tolerance
Dont compute cell average on artificial cells. Interpolate cannot use ghosted vectors, hence use right_hand_side. eps must be global minimum.
We cannot write into current_solution since it is a ghosted vector.
Fixed RK update and predictor update. We cannot write into ghosted vectors.
Merge pull request #8 from cpraveen/master

Fixed RK update and predictor update. We cannot write into ghosted vectors