Downgrade support tooling to allow building on Ubuntu 16.04

Gemfile.lock

@@ -1,13 +1,11 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    addressable (2.8.7)
-      public_suffix (>= 2.0.2, < 7.0)
     arr-pm (0.0.12)
-    backports (3.25.0)
+    backports (3.23.0)
     cabin (0.9.0)
     clamp (1.0.1)
-    dotenv (2.8.1)
+    dotenv (2.7.6)
     fpm (1.14.1)
       arr-pm (~> 0.0.11)
       backports (>= 2.6.2)
@@ -18,11 +16,10 @@ GEM
       pleaserun (~> 0.0.29)
       rexml
       stud
-    git (1.19.1)
-      addressable (~> 2.8)
+    git (1.11.0)
       rchardet (~> 1.8)
     insist (1.0.0)
-    json (2.8.2)
+    json (2.6.1)
     mustache (0.99.8)
     pleaserun (0.0.32)
       cabin (> 0)
@@ -31,10 +28,9 @@ GEM
       insist
       mustache (= 0.99.8)
       stud
-    public_suffix (5.1.1)
-    rake (13.2.1)
+    rake (13.0.6)
     rchardet (1.8.0)
-    rexml (3.3.9)
+    rexml (3.2.5)
     stud (0.0.23)
 
 PLATFORMS