Move KeywordMute into Glitch namespace.

There are two motivations for this:

1. It looks like we're going to add other features that require
   server-side storage (e.g. user notes).

2. Namespacing glitchsoc modifications is a good idea anyway: even if we
   do not end up doing (1), if upstream introduces a keyword-mute feature
   that also uses a "KeywordMute" model, we can avoid some merge
   conflicts this way and work on the more interesting task of
   choosing which implementation to use.

spec/models/glitch/keyword_mute_spec.rb

@@ -1,15 +1,15 @@
 require 'rails_helper'
 
-RSpec.describe KeywordMute, type: :model do
+RSpec.describe Glitch::KeywordMute, type: :model do
   let(:alice) { Fabricate(:account, username: 'alice').tap(&:save!) }
   let(:bob) { Fabricate(:account, username: 'bob').tap(&:save!) }
 
   describe '.matcher_for' do
-    let(:matcher) { KeywordMute.matcher_for(alice) }
+    let(:matcher) { Glitch::KeywordMute.matcher_for(alice) }
 
-    describe 'with no KeywordMutes for an account' do
+    describe 'with no Glitch::KeywordMutes for an account' do
       before do
-        KeywordMute.delete_all
+        Glitch::KeywordMute.delete_all
       end
 
       it 'does not match' do
@@ -17,63 +17,63 @@ RSpec.describe KeywordMute, type: :model do
       end
     end
 
-    describe 'with KeywordMutes for an account' do
+    describe 'with Glitch::KeywordMutes for an account' do
       it 'does not match keywords set by a different account' do
-        KeywordMute.create!(account: bob, keyword: 'take')
+        Glitch::KeywordMute.create!(account: bob, keyword: 'take')
 
         expect(matcher =~ 'This is a hot take').to be_falsy
       end
 
       it 'does not match if no keywords match the status text' do
-        KeywordMute.create!(account: alice, keyword: 'cold')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'cold')
 
         expect(matcher =~ 'This is a hot take').to be_falsy
       end
 
       it 'considers word boundaries when matching' do
-        KeywordMute.create!(account: alice, keyword: 'bob', whole_word: true)
+        Glitch::KeywordMute.create!(account: alice, keyword: 'bob', whole_word: true)
 
         expect(matcher =~ 'bobcats').to be_falsy
       end
 
       it 'matches substrings if whole_word is false' do
-        KeywordMute.create!(account: alice, keyword: 'take', whole_word: false)
+        Glitch::KeywordMute.create!(account: alice, keyword: 'take', whole_word: false)
 
         expect(matcher =~ 'This is a shiitake mushroom').to be_truthy
       end
 
       it 'matches keywords at the beginning of the text' do
-        KeywordMute.create!(account: alice, keyword: 'take')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'take')
 
         expect(matcher =~ 'Take this').to be_truthy
       end
 
       it 'matches keywords at the beginning of the text' do
-        KeywordMute.create!(account: alice, keyword: 'take')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'take')
 
         expect(matcher =~ 'This is a hot take').to be_truthy
       end
 
       it 'matches if at least one keyword case-insensitively matches the text' do
-        KeywordMute.create!(account: alice, keyword: 'hot')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'hot')
 
         expect(matcher =~ 'This is a HOT take').to be_truthy
       end
 
       it 'matches keywords surrounded by non-alphanumeric ornamentation' do
-        KeywordMute.create!(account: alice, keyword: 'hot')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'hot')
 
         expect(matcher =~ 'This is a ~*HOT*~ take').to be_truthy
       end
 
       it 'uses case-folding rules appropriate for more than just English' do
-        KeywordMute.create!(account: alice, keyword: 'großeltern')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'großeltern')
 
         expect(matcher =~ 'besuch der grosseltern').to be_truthy
       end
 
       it 'matches keywords that are composed of multiple words' do
-        KeywordMute.create!(account: alice, keyword: 'a shiitake')
+        Glitch::KeywordMute.create!(account: alice, keyword: 'a shiitake')
 
         expect(matcher =~ 'This is a shiitake').to be_truthy
         expect(matcher =~ 'This is shiitake').to_not be_truthy