Updated email hash to Gravatar specifications

Gravatar email hashes have two requirements:
* Whitespace must be trimmed
* Email should be downcased

app/models/user.rb

@@ -176,7 +176,7 @@ class User < ActiveRecord::Base
   end
 
   def self.email_hash(email)
-    Digest::MD5.hexdigest(email) 
+    Digest::MD5.hexdigest(email.strip.downcase)
   end
 
   def email_hash

spec/models/user_spec.rb

@@ -291,6 +291,22 @@ describe User do
     it 'should have a sane email hash' do
       @user.email_hash.should =~ /^[0-9a-f]{32}$/
     end
+
+    it 'should use downcase email' do
+      @user.email = "example@example.com"
+      @user2 = Fabricate(:user)
+      @user2.email = "ExAmPlE@eXaMpLe.com"
+
+      @user.email_hash.should == @user2.email_hash
+    end
+
+    it 'should trim whitespace before hashing' do
+      @user.email = "example@example.com"
+      @user2 = Fabricate(:user)
+      @user2.email = " example@example.com "
+
+      @user.email_hash.should == @user2.email_hash
+    end
   end
 
   describe 'name heuristics' do