Replace DisabledByDefault: true with disabling each cop (#26)

When `DisabledByDefault` is `true`, all cops in the default configuration.
This means that all extension cops are disabled by default.

The extensions are outside the scope of omakase, and you may not realize that it has been disabled.

rubocop.yml

@@ -8,10 +8,33 @@ inherit_mode:
 
 AllCops:
   SuggestExtensions: false
-  DisabledByDefault: true
   Exclude:
     - "data/**/*"
 
+# All cops except your using extensions are disabled by default.
+Bundler:
+  Enabled: false
+Gemspec:
+  Enabled: false
+Layout:
+  Enabled: false
+Lint:
+  Enabled: false
+Metrics:
+  Enabled: false
+Naming:
+  Enabled: false
+Performance:
+  Enabled: false
+  Exclude:
+    - "test/**/*"
+Rails:
+  Enabled: false
+Security:
+  Enabled: false
+Style:
+  Enabled: false
+
 # Align `when` with `end`.
 Layout/CaseIndentation:
   Enabled: true
@@ -152,10 +175,6 @@ Lint/RequireParentheses:
 Lint/UriEscapeUnescape:
   Enabled: true
 
-Performance:
-  Exclude:
-    - "test/**/*"
-
 Performance/FlatMap:
   Enabled: true