Update install.md

Add Windows default Eigen path.

Add notice saying that CMake will attempt to find Eigen automatically.
Update install.md

Reverting commit that was intended for the development branch. 

Oops.
added FindEigen3.cmake [*] and c11Support.cmake Changed CMakeLists.txt accordingly
* downloaded from https://bitbucket.org/eigen/eigen/src/12a658962d4e/cmake/FindEigen3.cmake
Update TODO
Removed unnecessary comments and fixed user not being able to specify eigen location
Removed warning flags, only c++11 support flags remaining
Enabled all tests
Merge branch 'development' of github.com:bgrimstad/multivariate-splines into development