Use JSON.load to instantiate errors

As of JSON 1.7.7, JSON.parse no longer instantiates json_class as
specified in the source document. JSON.load retains the original
behavior.

Gemfile.lock

@@ -23,7 +23,8 @@ GEM
       ffi (~> 1.0, >= 1.0.6)
     diff-lcs (1.1.2)
     ffi (1.2.0)
-    json (1.7.6)
+    ffi (1.2.0-x86-mingw32)
+    json (1.7.7)
     libwebsocket (0.1.7.1)
       addressable
       websocket
@@ -32,6 +33,7 @@ GEM
       subexec (~> 0.0.4)
     multi_json (1.5.0)
     nokogiri (1.5.6)
+    nokogiri (1.5.6-x86-mingw32)
     rack (1.4.1)
     rack-test (0.6.2)
       rack (>= 1.0)

lib/capybara/webkit/browser.rb

@@ -208,7 +208,7 @@ module Capybara::Webkit
       if result.nil?
         raise NoResponseError, "No response received from the server."
       elsif result != 'ok'
-        raise JSON.parse(read_response)
+        raise JSON.load(read_response)
       end
 
       result