FIX: shift+click on links

Default browser's behavior when shift+clicking was messed up.

This adds the shift key modifier to the list of click modifiers in both
`click_track` and `discourse`.

Also updated & refactored a bit the `click_track_spec`.
Merge pull request #796 from ZogStriP/fix-shift-clicks-on-links

FIX: shift+click on links
firefox used to display "loading..." on back sometimes
vagrant detection attempt
added option to force polling instead of messing with the detection
oops
:s/POST/REPLY/g
no_js to use site customisations
correct base url in emoji so I can close bug
simplify pinning message a bit
this is a slightly round about way of making our self oneboxes sane
shrunk avatar to 60px, added global whitelisting
Get Discourse ready for deployment

Signed-off-by: David Celis <me@davidcel.is>