update the regru-premailer gem

We have a fix on master that is not yet in a release gem

refs CNVS-7945

test plan: notifications should still be successfully sent in all situations,
such as replying to discussions. this new version of the gem also fixes
an issue where <img> tags weren't getting replaced with their alt text
in some situations, which is an unrelated bug "fix". this doesn't appear
to affect canvas negatively in my testing.

Change-Id: Idbf52aa006d04252b7870cd0a3208d7bdc0e20e3
Reviewed-on: https://gerrit.instructure.com/24024
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Jeremy Putnam <jeremyp@instructure.com>
Product-Review: Brian Palmer <brianp@instructure.com>

Gemfile

@@ -94,7 +94,9 @@ gem 'will_paginate',  '2.3.15'
 gem 'xml-simple',     '1.0.12', :require => 'xmlsimple'
 gem 'foreigner',      '0.9.2'
 gem 'crocodoc-ruby',  '0.0.1', :require => 'crocodoc'
-gem 'regru-premailer', '1.7.7', :require => 'premailer'
+# needs https://github.com/regru/premailer/commit/8d3ae698eff135011b19e1587a68c399ec97b185
+# we can go back to the gem once 1.7.8 is released
+gem 'regru-premailer', :require => 'premailer', :git => "https://github.com/regru/premailer.git", :ref => "08a73c70701f5d81bc4a5cf6c959a45ad94db88e"
 
 group :assets do
   gem 'compass-rails', '1.0.3'

spec/lib/text_helper_spec.rb

@@ -296,6 +296,8 @@ describe TextHelper do
         -----------------
 
         Link to Foo ( http://foo.com )
+
+        Some Image
       END
     end
 
@@ -318,7 +320,9 @@ describe TextHelper do
         <br/>
         This is an h6 tag<br/>
         <br/>
-        Link to Foo ( <a href='http://foo.com'>http://foo.com</a> )</p>
+        Link to Foo ( <a href='http://foo.com'>http://foo.com</a> )<br/>
+        <br/>
+        Some Image</p>
       END
     end