Update Prometheus Gem to fix problem caused by reading bad data.

Gemfile

@@ -281,7 +281,7 @@ group :metrics do
   gem 'influxdb', '~> 0.2', require: false
 
   # Prometheus
-  gem 'prometheus-client-mmap', '~>0.7.0.beta17'
+  gem 'prometheus-client-mmap', '~>0.7.0.beta18'
   gem 'raindrops', '~> 0.18'
 end
 

Gemfile.lock

@@ -623,7 +623,7 @@ GEM
       parser
       unparser
     procto (0.0.3)
-    prometheus-client-mmap (0.7.0.beta17)
+    prometheus-client-mmap (0.7.0.beta18)
       mmap2 (~> 2.2, >= 2.2.7)
     pry (0.10.4)
       coderay (~> 1.1.0)
@@ -1106,7 +1106,7 @@ DEPENDENCIES
   pg (~> 0.18.2)
   poltergeist (~> 1.9.0)
   premailer-rails (~> 1.9.7)
-  prometheus-client-mmap (~> 0.7.0.beta17)
+  prometheus-client-mmap (~> 0.7.0.beta18)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
   rack-attack (~> 4.4.1)