Merge branch 'rs-bump-nokogiri' into 'master'

Explicitly require Nokogiri 1.6.7.1 due to security issue

```
Name: nokogiri
Version: 1.6.7
Advisory: CVE-2015-5312
Criticality: High
URL: https://groups.google.com/forum/#!topic/ruby-security-ann/aSbgDiwb24s
Title: Nokogiri gem contains several vulnerabilities in libxml2
Solution: upgrade to >= 1.6.7.1
```

See merge request !2154

Gemfile

@@ -101,6 +101,9 @@ gem 'wikicloth',     '0.8.1'
 gem 'asciidoctor',   '~> 1.5.2'
 gem 'rouge',         '~> 1.10.1'
 
+# See https://groups.google.com/forum/#!topic/ruby-security-ann/aSbgDiwb24s
+gem 'nokogiri', '1.6.7.1'
+
 # Diffs
 gem 'diffy', '~> 3.0.3'
 

Gemfile.lock

@@ -420,7 +420,7 @@ GEM
       grape
       newrelic_rpm
     newrelic_rpm (3.9.4.245)
-    nokogiri (1.6.7)
+    nokogiri (1.6.7.1)
       mini_portile2 (~> 2.0.0.rc2)
     nprogress-rails (0.1.6.7)
     oauth (0.4.7)
@@ -888,6 +888,7 @@ DEPENDENCIES
   net-ssh (~> 3.0.1)
   newrelic-grape
   newrelic_rpm (~> 3.9.4.245)
+  nokogiri (= 1.6.7.1)
   nprogress-rails (~> 0.1.6.7)
   oauth2 (~> 1.0.0)
   octokit (~> 3.7.0)