Update health_check rubygem to latest upstream release

Gemfile

@@ -440,7 +440,7 @@ gem 'activerecord-explain-analyze', '~> 0.1', require: false
 gem 'oauth2', '~> 1.4'
 
 # Health check
-gem 'health_check', '~> 2.6.0'
+gem 'health_check', '~> 3.0'
 
 # System information
 gem 'vmstat', '~> 2.3.0'

Gemfile.lock

@@ -518,8 +518,8 @@ GEM
     hashie (3.6.0)
     hashie-forbidden_attributes (0.1.1)
       hashie (>= 3.0)
-    health_check (2.6.0)
-      rails (>= 4.0)
+    health_check (3.0.0)
+      railties (>= 5.0)
     heapy (0.1.4)
     hipchat (1.5.2)
       httparty
@@ -1283,7 +1283,7 @@ DEPENDENCIES
   hamlit (~> 2.11.0)
   hangouts-chat (~> 0.0.5)
   hashie-forbidden_attributes
-  health_check (~> 2.6.0)
+  health_check (~> 3.0)
   hipchat (~> 1.5.0)
   html-pipeline (~> 2.12)
   html2text