Rebase for DataDog#292 - fixes HOSTNAME_EXTRACTION_REGEX reinit (DataDog#310)

* [gitignore] Gemfile.lock, ignore thy.

* Fixing 'already initialized constant' warnings

Author: truthbk

.gitignore

@@ -3,3 +3,4 @@ spec/fixtures
 .rspec_system
 .bundle
 vendor
+Gemfile.lock

lib/puppet/reports/datadog_reports.rb

@@ -15,11 +15,11 @@
   API_KEY = config[:datadog_api_key]
 
   # if need be initialize the regex
-  HOSTNAME_EXTRACTION_REGEX = config[:hostname_extraction_regex]
+  HOSTNAME_REGEX = config[:hostname_extraction_regex]
   begin
-    HOSTNAME_EXTRACTION_REGEX = Regexp.new HOSTNAME_EXTRACTION_REGEX unless HOSTNAME_EXTRACTION_REGEX.nil?
+    HOSTNAME_EXTRACTION_REGEX = Regexp.new HOSTNAME_REGEX unless HOSTNAME_REGEX.nil?
   rescue
-    raise(Puppet::ParseError, "Invalid hostname_extraction_regex #{HOSTNAME_EXTRACTION_REGEX}")
+    raise(Puppet::ParseError, "Invalid hostname_extraction_regex #{HOSTNAME_REGEX}")
   end
 
   desc <<-DESC