Release version 1.5.5 with plugin version 0.4.11

Also bumps rubygems to 2.4 since 2.2 appears to have a bug processing
specs containing both >= and <= (it incorrectly included the wrong version
of one of the dependencies).

config/projects/google-fluentd.rb

@@ -8,15 +8,15 @@
 description "Google Fluentd: A data collector for Google Cloud Logging"
 
 install_dir     "/opt/google-fluentd"
-build_version   "1.5.4"
+build_version   "1.5.5"
 build_iteration 1
 
 # creates required build directories
 dependency "preparation"
 
 override :ruby, :version => '2.1.5'
 override :zlib, :version => '1.2.8'
-override :rubygems, :version => '2.2.1'
+override :rubygems, :version => '2.4.8'
 override :postgresql, :version => '9.3.5'
 
 # td-agent dependencies/components

plugin_gems.rb

@@ -16,4 +16,4 @@
 download "fluent-plugin-webhdfs", "0.4.1"
 download "fluent-plugin-rewrite-tag-filter", "1.4.1"
 download "fluent-plugin-td-monitoring", "0.2.1"
-download "fluent-plugin-google-cloud", "0.4.10"
+download "fluent-plugin-google-cloud", "0.4.11"