Simple kalman filter using blaze-lib

This is a starting point to compare other ways of implementing Kalman filters,
like those tuned by hand with SIMD instructions etc.
Added link to install instructions as well as mentioning boost as requirement
Multiple changes.
Move timer to separate file. Implement the Kalman filter using the
eigen3 library.
At this point, the Makefile is a mess :/ Maybe we should consider using
CMake as it has mechanisms for finding libraries on different systems
easily. I know that this can in theory also be achieved by using
autotools but I don't know how...
Update kalman_eigen.cpp
Adjust makefile according to the comments in #7.
Adjust readme according to the comments in #7.
Find eigen3 via pkg-config.
Rename for consistency.
Adjust makefile accordingly.
Merge pull request #7 from betatim/kalman

Implement a basic Kalman filter using different libraries for comparison.