first release targeting only USC students

MVP

Basic functions implemented including

1. post new event
2. join event
3. quit event
4. cancel event
5. comment event
6. discuss event

Now events comments are mixed with discussions, should be split at next release.
TODOs:

1. create a new comment system to separate comments from discussions after event finalized
2. better design the notification system
3. better design the rating system
4. open it to more universities.