Krypy

Release with usability improvements. Several simplifications were made for an easier use of the functionality in `krypy.recycling`. No API changes have been made.

This is a feature- and bug fix update:
- new `linsys.TimedLinearSystem` that times all operations.
- more mature recycling strategies based on timings.
- more efficient computation of residual norms in `deflation.bound_pseudo` via `utils.get_residual_norms`.
- bug fixed in `deflation.Arnoldifyer`.

Now with deflation and recycling support.

**Beta release!**
- new API
- linear systems are now handled via the `linsys.LinearSystem` class
- `linsys.Minres` and `linsys.Gmres` now use `utils.Arnoldi`
- new `utils.Arnoldi` class features several orthogonalization algorithms:
- modified Gram-Schmidt
- iterated modified Gram-Schmit
- Lanczos
- Householder
- all solvers in `linsys` can return the corresponding Arnoldi relation
- new submodule `deflation` enables deflation with all solvers from `linsys`
- new submodule `recycling` provides methods for recycling data while solving a sequence of linear systems.