Bump petrify gem version

Gemfile

@@ -1,8 +1,6 @@
 source "https://rubygems.org/"
 ruby "2.3.1"
 
-gem 'haml'
 gem 'data_mapper'
-gem 'dm-postgres-adapter'
-gem 'pg'
-gem 'petrify', git: 'https://github.com/adrianshort/petrify/'
+gem 'dm-sqlite-adapter'
+gem 'petrify', git: 'https://github.com/adrianshort/petrify/', ref: '04aa25b'

Gemfile.lock

@@ -1,8 +1,9 @@
 GIT
   remote: https://github.com/adrianshort/petrify/
-  revision: b1b04d7c3a7463e295d55703d5e2fa3288fa650a
+  revision: 04aa25b008188086ed1f4c79ebebfc9f6cbbd75d
+  ref: 04aa25b
   specs:
-    petrify (0.2.0)
+    petrify (0.3.0)
       haml
 
 GEM