Add release-notest recipe

Fix gradient calculation in ParallelProjector

Remove CLI argument '-allow-unsupported-compiler' for nvcc

Merge pull request #4 from theHamsta/parallel-beam

Parallel beam

Fix flipped sign

Force pushing of tasks

Save state also for backward pass

Fix backward projection

Skip pyconrad test not only on CI but always if pyconrad is not insta…

…lled

Avoid copying of projection_matrices on each kernel call