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
Fix GUI
Finish survey.removeRatings()
Remove manage.bat
Add subjective and objective sentences in examples.py
Add another objective sentence
Add more sentennces
Add features.py
Rename and refactor feature_extraction.py
Add example subjectivity classifier
Fix warnings for boolean fields
Set correct URL for survey (/survey)
Refactor urls
Implement student name should display