Odtbrain

- Code optimization (speed, memory) with numexpr
- New keyword argument `save_memory` for 3D reconstruction
on machines with limited memory
- New keyword argument `copy` for 3D reconstruction to protect
input sinogram data.

- The exponential term containing the distance between center
of rotation and detector `lD` is now multiplied with
the factor `M-1` instead of `M`. This is necessary,
because usually the scattered wave is normalized in both
amplitude and phase (`u_0`) and not only amplitude `a_0`
- Allow angles of shape (A,1) in `backpropagate_3d_tilted`
- Set default value lD=0 for all reconstruction algorithms
- Improvement of documentation

- Fixes for `backpropagate_3d_tilted` when `angles` are
points on the unit sphere:
- Make sure each point is normalized
- Correctly rotate each point w.r.t. `tilted_axis`

- Added reconstruction algorithm for tilted axis of rotation

- Support NumPy 1.10.
- Allow to weight backpropagation using keyword `weight_angles`
- Bugfix: backpropagate_3d with keyword `onlyreal=True` did not work
- Bugfix: sum_2d did not return correctly shaped array
- Code coverage is now 90%
- Added more examples to the documentation