Bug fixes and a few more features.

What's Changed

• addresses case where cluster has 2 orientations by @joelvbernier in #381
• Simulated peak by @saransh13 in #331
• routines to get absorption length of a material by @saransh13 in #380
• fixing issues with spline background estimation by @saransh13 in #383
• Move generating parameter names into a function by @psavery in #384
• Fix parameter names by @psavery in #385
• fixes to projection code by @joelvbernier in #386
• save two theta width in h5 file. by @saransh13 in #387
• Raw image imageseries by @donald-e-boyce in #388
• Rotations update by @joelvbernier in #391
• Update utils.py by @joelvbernier in #393
• Fix default material tThWidth for HDF5 by @psavery in #395
• Remove duplicate atom fix by @saransh13 in #394
• Fixing write error in material by @saransh13 in #396

Full Changelog: 0.8.17...0.8.18