Adding test for formatter

I have added database cleaner as for formatter spec it was trying to
use inbuild transactional fixture flag, which was failing as it
couldn't find any transaction to rollback. Hence switched to using
database_cleaner gem for using truncation as strategy

Gemfile.lock

@@ -38,6 +38,7 @@ GEM
     arel (3.0.3)
     builder (3.0.4)
     coderay (1.1.0)
+    database_cleaner (1.5.3)
     diff-lcs (1.2.5)
     erubis (2.7.0)
     generator_spec (0.9.3)
@@ -121,6 +122,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  database_cleaner
   generator_spec
   pry
   rspec-rails (~> 3.0)