Upgrade mail gem to remove dependency on mime-types.

* Use a EmailValidator.email_regexp for `Email.is_valid?`
  check as we're seeing an increase in allocation when
  parsing email addresses wih `Mail::Address`.

Gemfile

@@ -25,7 +25,6 @@ else
 end
 
 gem 'mail'
-gem 'mime-types', require: 'mime/types/columnar'
 gem 'mini_mime'
 gem 'mini_suffix'
 

Gemfile.lock

@@ -163,16 +163,13 @@ GEM
       crass (~> 1.0.2)
       nokogiri (>= 1.5.9)
     lru_redux (1.1.0)
-    mail (2.6.6)
-      mime-types (>= 1.16, < 4)
+    mail (2.7.0)
+      mini_mime (>= 0.1.1)
     memory_profiler (0.9.10)
     message_bus (2.1.2)
       rack (>= 1.1.3)
     metaclass (0.0.4)
     method_source (0.8.2)
-    mime-types (3.1)
-      mime-types-data (~> 3.2015)
-    mime-types-data (3.2016.0521)
     mini_mime (0.1.3)
     mini_portile2 (2.3.0)
     mini_racer (0.1.15)
@@ -445,7 +442,6 @@ DEPENDENCIES
   mail
   memory_profiler
   message_bus
-  mime-types
   mini_mime
   mini_racer
   mini_suffix

lib/email.rb

@@ -8,16 +8,7 @@ module Email
 
   def self.is_valid?(email)
     return false unless String === email
-
-    parsed = Mail::Address.new(email)
-
-    # Don't allow for a TLD by itself list (sam@localhost)
-    # The Grammar is: (local_part "@" domain) / local_part ... need to discard latter
-    parsed.address == email &&
-    parsed.local != parsed.address &&
-    parsed&.domain.split(".").size > 1
-  rescue Mail::Field::ParseError
-    false
+    !!(EmailValidator.email_regex =~ email)
   end
 
   def self.downcase(email)