change fpm to version 1.10.0 to fix the error in building wf-proxy-bu…

…ilder docker image

pkg/Dockerfile

@@ -9,7 +9,7 @@ RUN curl -L get.rvm.io | bash -s stable
 ENV PATH /usr/local/rvm/gems/ruby-1.9.3-p551/bin:/usr/local/rvm/gems/ruby-1.9.3-p551@global/bin:/usr/local/rvm/rubies/ruby-1.9.3-p551/bin:/usr/local/rvm/bin:$PATH
 ENV LC_ALL en_US.UTF-8
 RUN rvm install 1.9.3
-RUN gem install fpm --version 1.6.2
+RUN gem install fpm --version 1.10.0
 RUN gem install package_cloud --version 0.2.35
 
 # Wavefront software. This repo contains build scripts for the agent, to be run