Fix two places where we should be using `Rails.env.development?`

app/views/layouts/_head.html.haml

@@ -16,7 +16,7 @@
 
   = render 'layouts/google_analytics' if extra_config.has_key?('google_analytics_id')
   = render 'layouts/piwik' if extra_config.has_key?('piwik_url') && extra_config.has_key?('piwik_site_id')
-  = render 'layouts/bootlint' if Rails.env == 'development'
+  = render 'layouts/bootlint' if Rails.env.development?
 
   -# Atom feed
   - if current_user

config/initializers/6_rack_profiler.rb

@@ -1,4 +1,4 @@
-if Rails.env == 'development'
+if Rails.env.development?
   require 'rack-mini-profiler'
 
   # initialization is skipped so trigger it