motion: added { for movement to previous paragraph

* implemented `{` for movement to the previous paragraph
* added visual mode bindings for paragraph movement
Add gt, gT keybindings to switch tabs
Merge pull request #76 from zenhob/move-to-previous-paragraph

motion: move to previous paragraph
Add changelog notes for #76
Merge pull request #59 from JosephKu/master

Add gt, gT keybindings to switch tabs
Add changelog note for #59
Merge branch 'master' into search-is-a-motion

Conflicts:
	lib/motions.coffee
Bring some of the tests up to date