Pin rexml version (temporary workaround for rexml #131)

Author: alextwoods

Gemfile

@@ -13,7 +13,7 @@ gem 'jmespath'
 gem 'json'
 gem 'nokogiri', '>= 1.6.8.1'
 gem 'oga'
-gem 'rexml'
+gem 'rexml', '= 3.2.6' # Temporary Workaround (https://github.com/ruby/rexml/issues/131)
 
 # These json and xml parsers do not have java gems
 unless defined?(JRUBY_VERSION)