Try this

Author: bobtfish

Gemfile

@@ -1,4 +1,6 @@
 source 'https://rubygems.org'
 
+gem 'docker-api', :require => 'docker'
+
 # Specify your gem's dependencies in synapse.gemspec
 gemspec

Gemfile.lock

@@ -4,6 +4,7 @@ PATH
     synapse (0.12.1)
       aws-sdk (~> 1.39)
       docker-api (~> 1.7.2)
+      etcd (~> 0.2.4)
       zk (~> 1.9.4)
 
 GEM
@@ -21,6 +22,8 @@ GEM
       archive-tar-minitar
       excon (>= 0.28)
       json
+    etcd (0.2.4)
+      mixlib-log
     excon (0.45.4)
     ffi (1.9.3-java)
     json (1.8.3)
@@ -30,6 +33,7 @@ GEM
       multi_json (>= 1.8.4)
     method_source (0.8.2)
     mini_portile (0.6.2)
+    mixlib-log (1.6.0)
     multi_json (1.11.2)
     nokogiri (1.6.6.2)
       mini_portile (~> 0.6.0)
@@ -70,11 +74,9 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  docker-api
   pry
   pry-nav
   rake
   rspec (~> 3.1.0)
   synapse!
-
-BUNDLED WITH
-   1.10.5

synapse.gemspec

@@ -17,7 +17,7 @@ Gem::Specification.new do |gem|
   gem.test_files    = gem.files.grep(%r{^(test|spec|features)/})
 
   gem.add_runtime_dependency "aws-sdk", "~> 1.39"
-  gem.add_runtime_dependency "docker-api", "~> 1.7.2"
+  gem.add_runtime_dependency 'docker-api', "~> 1.7.2"
   gem.add_runtime_dependency "zk", "~> 1.9.4"
   gem.add_runtime_dependency "etcd", "~> 0.2.4"