Upgrade httpclient gem from 2.7.0.1 to 2.8.2.

Fixes deprecation warnings from Ruby 2.3.

Changelog: https://github.com/nahi/httpclient/blob/b51d7a8bb78f71726b08fbda5abfb900d627569f/CHANGELOG.md#changes-in-282

Gemfile.lock

@@ -338,7 +338,7 @@ GEM
     httparty (0.13.7)
       json (~> 1.8)
       multi_xml (>= 0.5.2)
-    httpclient (2.7.0.1)
+    httpclient (2.8.2)
     i18n (0.7.0)
     ice_nine (0.11.1)
     influxdb (0.2.3)