Bump poltergeist

Gemfile

@@ -283,7 +283,7 @@ group :test do
 
   gem "capybara",           "2.14.4"
   gem "database_cleaner",   "1.6.1"
-  gem "poltergeist",        "1.13.0"
+  gem "poltergeist",        "1.15.0"
 
   gem "cucumber-api-steps", "0.13", require: false
 

Gemfile.lock

@@ -434,7 +434,7 @@ GEM
       ast (~> 2.2)
     pg (0.21.0)
     phantomjs (2.1.1.0)
-    poltergeist (1.13.0)
+    poltergeist (1.15.0)
       capybara (~> 2.1)
       cliver (~> 0.3.1)
       websocket-driver (>= 0.2.0)
@@ -824,7 +824,7 @@ DEPENDENCIES
   open_graph_reader (= 0.6.2)
   openid_connect (= 1.1.2)
   pg (= 0.21.0)
-  poltergeist (= 1.13.0)
+  poltergeist (= 1.15.0)
   pronto (= 0.9.4)
   pronto-eslint (= 0.9.1)
   pronto-haml (= 0.9.0)