Add email validator

#186

lib/validators/email_validator.rb

@@ -0,0 +1,15 @@
+class EmailValidator
+  def self.regexp
+    Devise::email_regexp
+  end
+
+  def initialize(email)
+    @email = email
+  end
+
+  def valid?
+    email =~ self.class.regexp
+  end
+
+  attr_reader :email
+end