Add dragonfly dependency

Gemfile.lock

@@ -2,7 +2,8 @@ PATH
   remote: .
   specs:
     simplest_photo (0.0.1)
-      rails (~> 4.2.1)
+      dragonfly
+      rails (>= 4.2.1)
 
 GEM
   remote: https://rubygems.org/
@@ -42,8 +43,13 @@ GEM
       minitest (~> 5.1)
       thread_safe (~> 0.3, >= 0.3.4)
       tzinfo (~> 1.1)
+    addressable (2.3.8)
     arel (6.0.0)
     builder (3.2.2)
+    dragonfly (1.0.9)
+      addressable (~> 2.3)
+      multi_json (~> 1.0)
+      rack
     erubis (2.7.0)
     globalid (0.3.5)
       activesupport (>= 4.1.0)
@@ -56,6 +62,7 @@ GEM
     mime-types (2.5)
     mini_portile (0.6.2)
     minitest (5.6.1)
+    multi_json (1.11.0)
     nokogiri (1.6.6.2)
       mini_portile (~> 0.6.0)
     rack (1.6.1)

simplest_photo.gemspec

@@ -14,10 +14,11 @@ Gem::Specification.new do |s|
   s.description = ""
   s.license     = "MIT"
 
-  s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
+  s.files      = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
   s.test_files = Dir["test/**/*"]
 
-  s.add_dependency "rails", "~> 4.2.1"
+  s.add_dependency "rails", ">= 4.2.1"
+  s.add_dependency "dragonfly"
 
   s.add_development_dependency "sqlite3"
 end