Revert "Upgrade select2.js to 79b5bf6db"

This reverts commit 4400040360b78cf4bf4f27561169468b27fabc55.

The select2 upgrade erroneously removed the 'add all current
selections' functionality that was added specifically. Upgrade adds no
features, removes features, therefore, revert.
Merge pull request #21 from anchor/select2_revert

Revert select2.js upgrade
Remove all instances of @metrics with global gon

It's not very useful having multiple sources of truth of what a metric
is. Since we're now using gon to store more than just a metric list, and
with the changes to metric id and metric meta, it makes sense to use
gon as the one source of truth

Since gon isn't available by default in ruby embedded within views, I've
opted to copy the gon param into @gon for these cases. Small alterations
to which metric type (id/metric) also apply.

Reordering of /index logic is to handle requirement to have a list of
metrics before any flash errors (@graph assignment used to flag the fact
we should graph things, so this appear after all possible error points)
Merge branch 'master' into kill_atmetric
Merge branch 'addr' into kill_atmetric
Merge pull request #23 from anchor/kill_atmetric

Remove all instances of @metrics with global gon