Open external links in browser

If a clicked links host doesn't match www.trello.com or trello.com it
will be opened with the default browser.
click dock icon to reopen the window
window now remembers location and size
Update README.md
Add Refresh Menu Button
Merge remote-tracking branch 'dovizu/master'
Merge remote-tracking branch 'reneretz/master'

Conflicts:
	Trello/en.lproj/MainMenu.xib
Target 10.9