Update vmstat for {Open,Net}BSD support

Gemfile

@@ -349,5 +349,5 @@ gem 'paranoia', '~> 2.0'
 gem 'health_check', '~> 2.1.0'
 # System information
-gem 'vmstat', '~> 2.1.1'
+gem 'vmstat', '~> 2.2'
 gem 'sys-filesystem', '~> 1.1.6'

Gemfile.lock

@@ -772,7 +772,7 @@ GEM
       coercible (~> 1.0)
       descendants_tracker (~> 0.0, >= 0.0.3)
       equalizer (~> 0.0, >= 0.0.9)
-    vmstat (2.1.1)
+    vmstat (2.2.0)
     warden (1.2.6)
       rack (>= 1.0)
     web-console (2.3.0)
@@ -980,7 +980,7 @@ DEPENDENCIES
   unicorn-worker-killer (~> 0.4.2)
   version_sorter (~> 2.1.0)
   virtus (~> 1.0.1)
-  vmstat (~> 2.1.1)
+  vmstat (~> 2.2)
   web-console (~> 2.0)
   webmock (~> 1.21.0)
   wikicloth (= 0.8.1)