add gitcafe as silver sponsor; add boohee as bronze sponsor.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	source/index.html.erb
a href for speakers' companies
add venue info
Merge pull request #2 from jasl/venue

添加了会场联系人信息
Merge branch 'master' of github.com:ruby-china/rubyconfchina.org
Merge pull request #1 from yujingz/master

a href for speakers' companies
add more speakers
Merge remote-tracking branch 'rubyconf/master'
add the speaker
adjust sponsors' logo size.
limit max-width of sponsors' logos.
change favicon.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	source/index.html.erb
Adjustment position of bitfund.
Remove speaker: Vincent.
add jingdong and github as sponsors.
Merge remote-tracking branch 'upstream/master'
Update url of JD
Fix typo