Change _rk_stages to _registers
Add SSPMS(3,2) and general linear multistep time-discretization.
Edit linear multistep methods.
Adding variable time-step functionality to SSPMS32, editing LMM, adding a dictionary for ssp coefficients in sharpclaw class.
Corrections so that classic solver runs.
Change _rk_stages to _registers
Add SSPMS(3,2) and general linear multistep time-discretization.
Edit linear multistep methods.
Adding variable time-step functionality to SSPMS32, editing LMM, adding a dictionary for ssp coefficients in sharpclaw class.
Corrections so that classic solver runs.
Introduce generic functions for cfl_max and dt_new.
Merging from ketch/linear_multistep_methods.
Adding sspcoeff = None for 'RK' and 'LMM' so that nosetests run.
Add check to see if pickle file actually exists

If this fails it does not replace the default mapc2p.
Add temporary problem data  values
Merge pull request #371 from mandli/fix-pickle-problem

Fix ascii pickle problem
Set default cfl_desired and cfl_max to 'None'. Values are assigned in setup according to time-discretization.
Add tests for SSPMS32 method (for advection 1D, acoustics 1D and 2D).
Set default time_integrator to 'SSP104'.
Remove return in _allocate_registers.