category dropdown, sticky footer
Merge branch 'dev_xiaoli'

* dev_xiaoli:
  category dropdown, sticky footer

Conflicts:
	src/index.html
	src/loginpage.php
	src/signuppage.php
	src/sorter.php
Fix sticky footer problem
Merge pull request #19 from jennjwu/dev_xiaoli

Fix sticky footer problem
add login function (extra index.php to handle session)
fix merge conflict