ENH: Derivatives in python compilers + numexpr code merge
Doc update.
Added function to plot decision rules. Import it by default.
Some update to interpolation routines.
Added Rouwenhorst to discretization options.
Bugfix for theano compilation.
Some temporary changes in interpolation.
Moved version number.
REF: the package now officially depends on cython and there is only one setup file.
FIX: parameters were ignored in newton solver + removed old junk
Removed old files.
ENH: new cython interpolation routines