Revert "add Author, Review and Sentence models in models.py"

This reverts commit f80b4c68a50142a554ba874cb789661dd1b36c02.
Revert "Revert "add Author, Review and Sentence models in models.py""

This reverts commit 0bb57761e0592b22cf8e4d2dd92159a997384fac.
Merge branch 'francis' of https://www.github.com/arkeidolon/sarprit into francis
Merge branch 'francis' of https://www.github.com/arkeidolon/sarprit into francis
Merge branch 'francis' of https://www.github.com/arkeidolon/sarprit into francis
Merge branch 'francis' of https://www.github.com/arkeidolon/sarprit into francis
Merge branch 'master' of https://www.github.com/arkeidolon/sarprit into francis
Merge branch 'master' into francis
Text parser for batch adding students in /students
Improve model string representations
Ajax for student models at /admin/students/ (every 10 seconds)