Removed duplicated entries in gitignore file. Updated ICs for 2D Sod shock (See #278). Reduced max_dt for 1D sedov explosion

Added pressure to entropy and pressure to internal energy functions to the equation of state definition.

Include @bvandenbroucke's typo corrections in dimension.h as well as the sphere to radius calculation functions.

Added actual grid test to testVoronoi3D; degenerate case crashes. Started documenting 3D Voronoi algorithm to refresh my memory about how it works.

Fixed wrong box size in 2D Sod shock that caused SHADOWFAX_SPH to crash. Added flag in const.h to enable or disable cell motion steering. Made sure cell centroids have all their coordinates initialized.

Fixed bug in 2D Voronoi algorithm. Sod shock now works (with fixed cells). Moved gradient and slope limiter defines for SHADOWFAX_SPH to const.h.

Fixed small mistake in 2D Voronoi neighbour calculation. Added check for neighbour relations to unit test.

Realized I forgot to implement neighbour relations in 2D Voronoi algorithm. Implemented them. 2D Sod shock still doesn't work.

Fixed a bug in 2D Voronoi algorithm, added a lot of debugging output possibilities. 2D algorithm now works for 100 uniform random generators in a periodic box.

Finished first part of 2D Voronoi intersection algorithm. Now *only* need to write the second part. And maybe deal with degeneracies...

3D SHADOWFAX_SPH compiles again (but does not really work). Re-introduced global variables to store the box size.

Cleaned up 1D Voronoi algorithm some more. Added SHADOWFAX_TOTAL_ENERGY flag and support for an isothermal EoS.

Timebin optimization

This implements a change to the active/inactive checks following @jwillis' remark that the code was a bit slower than in the old master he was working on. 

The idea is to pre-compute the largest active time-bin and then use this information to decide whether act on particles or not. The old scheme was computing the end-time of the particle which involves a lot more information for the same result.

See merge request !316

Made all python scripts numpy 1.8.2 compatible, and fixed some bugs while doing it.

Title says it all. This should close #272.

See merge request !319

Cleaned up GIZMO code, added SineWavePotential tests.

The GIZMO code should now be clean enough to merge with `master`, and to be used in scaling tests.

I have added 1-3D versions of a new SineWavePotential test, which tests gravitational hydrostatic equilibrium in an unphysical but convenient 1D periodic sine wave potential. This allows testing gravity + GIZMO hydro without running into boundary condition problems. Unfortunately, the non conservative form of the potential makes it impossible to test energy conservation in these tests. GIZMO can keep all three set ups stable with both an isothermal and an ideal gas equation of state. I have currently only tested with the exact Riemann solver, but the approximate solvers should work as well.

The code is still not stable enough to cope with the hydrostatic and disc patch tests; these are next on my list.

See merge request !317