Adding Cython and pure Python general Kalman Filter estimators.
Added methods separating the iteration of the Kalman filter from its setup.
Fixed issues with Kalman filter and added the initial values as optional arguments.
Refactored python kalman filter; added versions for single precision, double precision, complex, and double precision complex.
FIX: Fixed problem with calculating initial values.
ENH: Added blas functions for copying data (dcopy) and for multiplying symmetric matrices (dsymm) for double precision reals.
DOC: Fix typo
ENH: Added *copy and *symm BLAS functions for faster data copying and symmetric matrix multiplication.
FIX: *symm BLAS functions not available prior to scipy 0.13. Replaced by *gemm calls for now.
FIX: Created single precision arrays correctly.
FIX: Typo in zcopy function declaration.
ENH: Made weakly exogenous data z and associated parameter matrix A optional.
ENH: Allowed iterations to use simpler inversion calculation when n=1.
FIX: Fixed error in vector length using *copy.
ENH: Added Cholesky decomposition.
ENH: Improved performance by considering steady-stage convergence
FIX: Updated convergence tolerance so that unit tests pass.
ENH: Added storage of inverse prediction error covariance matrix.

This matrix is useful for smoothers.
ENH: Added support for non-positive definite covariance matrix of full state error term.
ENH: Added support for non-positive definite Q matrices.