Provide extension mechanism for UI tests
Bacon utils for Leaflet

* Rename wrapOnEvent() as leafletEventStream()
* Add leafletSingleClickEventStream()
* Add settings.DOUBLE_CLICK_INTERVAL and config.doubleClickInterval
Fixes #750, font-size issues
Use :empty to fix error message display
Fix broken UI tests
Make 'Tree Key' open in new tab

fixes #726 on github.
Merge pull request #765 from steventlamb/bug/726/tree_key_target_blank

Make 'Tree Key' open in new tab
Add tooltip to Additional Trunk '+' button

addresses #691 on github.

may or may not be a complete fix.
Add :empty on text-error inline form messages
Merge pull request #764 from mtedeschi/topic/post-launch-fixes

Last minute styling fixes
Merge pull request #763 from RickMohr/single-not-double-click

Bacon utils for Leaflet
Add semicolon.
Merge pull request #766 from steventlamb/bug/691/multiple_trunk_button_text

Add tooltip to Additional Trunk '+' button
Merge pull request #762 from ahinz/fix/ui-tests

Fix/ui tests
Fix lint