aliases/implications: remove 'pending' state.

Remove the pending status from tag aliases and implications.

Previously aliases would be created first in the pending state then
changed to active when the alias was later processed in a delayed job.
This meant that BURs weren't processed completely sequentially; first
all the aliases in a BUR would be created in one go, then later they
would be processed and set to active sequentially.

This was problematic in complex BURs that tried to reverse or swap
around aliases, since new pending aliases could be created before old
conflicting aliases were removed.

test/unit/artist_test.rb

@@ -94,7 +94,6 @@ class ArtistTest < ActiveSupport::TestCase
       end
 
       should "create a new tag implication" do
-        perform_enqueued_jobs
         assert_equal(1, TagImplication.where(:antecedent_name => "aaa", :consequent_name => "banned_artist").count)
         assert_equal("aaa banned_artist", @post.reload.tag_string)
       end