Update gem dependencies to latest stable versions

Gemfile

@@ -1,5 +1,6 @@
 source "https://rubygems.org"
 
-gem 'docker-api'
-gem 'rake'
-gem 'serverspec'
+gem 'docker-api', '~> 2.4'
+gem 'rake', '~> 13.0'
+gem 'rspec', '~> 3.13'
+gem 'serverspec', '~> 2.43'

Gemfile.lock

@@ -0,0 +1,52 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    base64 (0.3.0)
+    diff-lcs (1.6.2)
+    docker-api (2.4.0)
+      excon (>= 0.64.0)
+      multi_json
+    excon (0.109.0)
+    multi_json (1.15.0)
+    net-scp (4.1.0)
+      net-ssh (>= 2.6.5, < 8.0.0)
+    net-ssh (7.3.0)
+    net-telnet (0.2.0)
+    rake (13.3.1)
+    rspec (3.13.2)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-its (1.3.1)
+      rspec-core (>= 3.0.0)
+      rspec-expectations (>= 3.0.0)
+    rspec-mocks (3.13.7)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-support (3.13.7)
+    serverspec (2.43.0)
+      multi_json
+      rspec (~> 3.0)
+      rspec-its
+      specinfra (~> 2.72)
+    sfl (2.3)
+    specinfra (2.94.1)
+      base64
+      net-scp
+      net-ssh (>= 2.7)
+      net-telnet
+      sfl
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  docker-api (~> 2.4)
+  rake (~> 13.0)
+  rspec (~> 3.13)
+  serverspec (~> 2.43)