Remove rubocop and eslint from CodeClimate

This was causing issues with the difference in version between
CodeClimate and our style checking task so we're just turning it off.
Note that all the other engines needed to be kept enabled explicitly.

Also removed ESLint since we don't really use it.

Author: orenyk

.codeclimate.yml

@@ -0,0 +1,12 @@
+engines:
+  brakeman:
+    enabled: true
+  bundler-audit:
+    enabled: true
+  duplication:
+    enabled: true
+  fixme:
+    enabled: true
+  rubocop:
+    enabled: false
+