relax 1.0.6

Description

This release includes both added features and bug fixes. The Euler angle β of the diffusion tensor is now treated as a glide reflection when between π and 2π rather than a translation of the space between 0 and π. The glide reflection and translation symmetries of the spheroid and ellipsoid diffusion tensors are now collapsed such that all angles are between 0 and π, and the simulated values lie π/2 either side of the fitted value.