documentation updates 

Merge pull request yzhao062#206 from yzhao062/development V 0.8.1

Merge pull request yzhao062#185 from yzhao062/development v0.7.9

Merge pull request yzhao062#168 from yzhao062/development V0.7.8 Bug Fixes and New Models (VAE and LODA)

Merge pull request yzhao062#151 from yzhao062/development V0.7.6

Merge pull request yzhao062#136 from yzhao062/development V 0.7.5

Merge pull request yzhao062#62 from marcelflygare/patch-1 Update pca.py

Update doc structure 

Update README.rst 

Pre-release