Update static/css/main.scss

内容较少时，footer不在最底下。
Merge pull request #1 from uoryon/master

样式修正
更新文件，添加一些改动和修复。
remove .DS_Store, *.pyc and .sass-cache
remove .DS_Store, *.pyc and .sass-cache, *.swp
update dbstructure.
added requirements.txt and .gitignore.
changed README.md deployment 101.