adds icons for several tags, displays on event listings
removes trademarked logo icons
add logo attributions, extracted some logic to EventsHelper
further extracts icon display logic to EventsHelper
adds tests for tag icon EventsHelper methods
modifies specs to test individual elements of image tags rather than whole
scopes down tag icons specs to test only essentials
Merge pull request #239 from supremebeing7/tag_icons

adds icons for several tags, displays on event listings