refactored resizer to use imagemagick, fixed some tests

Gemfile.lock

@@ -85,8 +85,6 @@ GEM
     method_source (0.6.0)
       ruby_parser (>= 2.0.5)
     mime-types (1.16)
-    mini_magick (3.3)
-      subexec (~> 0.1.0)
     mocha (0.10.0)
       metaclass (~> 0.0.1)
     multi_json (1.0.3)
@@ -128,6 +126,7 @@ GEM
       thor (~> 0.14.6)
     rake (0.9.2)
     rdoc (3.9.4)
+    rmagick (2.13.1)
     ruby_parser (2.2.0)
       sexp_processor (~> 3.0)
     sexp_processor (3.0.6)
@@ -144,7 +143,6 @@ GEM
       hike (~> 1.2)
       rack (~> 1.0)
       tilt (!= 1.3.0, ~> 1.1)
-    subexec (0.1.0)
     super_exception_notifier (3.0.13)
       actionmailer
       rake
@@ -180,12 +178,12 @@ DEPENDENCIES
   mechanize
   memcache-client
   meta_search!
-  mini_magick
   mocha
   nokogiri
   pg
   pry
   rails (= 3.1.0)
+  rmagick
   sanitize!
   shoulda
   silent-postgres