Bump capistrano-maintenance from 1.0.0 to 1.2.0

Bumps [capistrano-maintenance](https://github.com/capistrano/maintenance) from 1.0.0 to 1.2.0.
- [Release notes](https://github.com/capistrano/maintenance/releases)
- [Changelog](https://github.com/capistrano/maintenance/blob/master/CHANGELOG.md)
- [Commits](capistrano/maintenance@v1.0.0...v1.2.0)

Gemfile.lock

@@ -75,7 +75,7 @@ GEM
     capistrano-bundler (1.1.4)
       capistrano (~> 3.1)
       sshkit (~> 1.2)
-    capistrano-maintenance (1.0.0)
+    capistrano-maintenance (1.2.0)
       capistrano (>= 3.0)
     capistrano-rails (1.1.3)
       capistrano (~> 3.1)
@@ -100,7 +100,6 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.9.1.1)
-    colorize (0.7.7)
     concurrent-ruby (1.1.5)
     crass (1.0.4)
     database_cleaner (1.5.0)
@@ -283,7 +282,7 @@ GEM
     multipart-post (2.0.0)
     net-scp (1.2.1)
       net-ssh (>= 2.6.5)
-    net-ssh (2.9.2)
+    net-ssh (5.2.0)
     nokogiri (1.8.5)
       mini_portile2 (~> 2.3.0)
     nokogiri (1.8.5-java)
@@ -378,8 +377,7 @@ GEM
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
     sqlite3 (1.3.10)
-    sshkit (1.7.1)
-      colorize (>= 0.7.0)
+    sshkit (1.18.2)
       net-scp (>= 1.1.2)
       net-ssh (>= 2.8.0)
     thor (0.20.3)