Adds in some basic AJAX

Adds in a basic ajax command for submitting posts (using jQuery)

Current issues: 
- [ ] No initial post filtering or smiley filtering on submit (only when page is refreshed and can thus go through PHP function)
- [ ] Currently console logs error messages from the AJAX - we need to do something with this
- [ ] AJAX doesn't fail if there is an error
- [ ] Display the Error message when there is an error

Good start for #15 though