Fix: 'Close Selected Tabs' not working in FF 29+

https://github.com/piroor/multipletab/issues/68
Merge pull request #69 from Rikk/patch-1

Fix: 'Close Selected Tabs' not working in FF 29+ (#68)
Add credits
Bump copyright year to 2014
Fix coding style
Fix wrong version of Firefox
Update history topics
Bump version to 0.7.2014042701
Bump maxVersion to 31.01a
Merge pull request #1 from piroor/master

sync