fix docker build

Dockerfile

@@ -4,7 +4,7 @@ MAINTAINER peng@sleede.com
 # First we need to be able to fetch from https repositories
 RUN apt-get update && \
     apt-get install -y apt-transport-https \
-      ca-certificates
+      ca-certificates apt-utils
 
 
 # Add sources for external tools to APT

Gemfile.lock

@@ -80,17 +80,6 @@ GEM
     builder (3.2.3)
     byebug (8.2.3)
     camertron-eprun (1.1.0)
-    capistrano (2.15.5)
-      highline
-      net-scp (>= 1.0.0)
-      net-sftp (>= 2.0.0)
-      net-ssh (>= 2.0.14)
-      net-ssh-gateway (>= 1.1.0)
-    capistrano-maintenance (0.0.5)
-      capistrano (~> 2.0)
-    capistrano-sidekiq (0.5.2)
-      capistrano
-      sidekiq
     carrierwave (0.10.0)
       activemodel (>= 3.2.0)
       activesupport (>= 3.2.0)
@@ -189,7 +178,6 @@ GEM
     hashdiff (0.3.0)
     hashery (2.1.2)
     hashie (3.5.7)
-    highline (1.7.1)
     hike (1.2.3)
     hitimes (1.2.2)
     htmlentities (4.3.4)
@@ -223,7 +211,6 @@ GEM
     kaminari (0.16.3)
       actionpack (>= 3.0.0)
       activesupport (>= 3.0.0)
-    kgio (2.9.3)
     libv8 (3.16.14.11)
     loofah (2.2.3)
       crass (~> 1.0.2)
@@ -257,13 +244,6 @@ GEM
     multi_xml (0.5.5)
     multipart-post (2.0.0)
     naught (1.1.0)
-    net-scp (1.2.1)
-      net-ssh (>= 2.6.5)
-    net-sftp (2.1.2)
-      net-ssh (>= 2.6.5)
-    net-ssh (2.9.2)
-    net-ssh-gateway (1.2.0)
-      net-ssh (>= 2.6.5)
     netrc (0.10.3)
     nokogiri (1.10.1)
       mini_portile2 (~> 2.4.0)
@@ -347,7 +327,6 @@ GEM
       rake (>= 0.8.7)
       thor (>= 0.18.1, < 2.0)
     rainbow (3.0.0)
-    raindrops (0.13.0)
     rake (12.3.2)
     rb-fsevent (0.9.4)
     rb-inotify (0.9.5)
@@ -381,8 +360,6 @@ GEM
     rubyzip (1.2.2)
     rufus-scheduler (3.0.9)
       tzinfo
-    rvm-capistrano (1.5.6)
-      capistrano (~> 2.15.4)
     safe_yaml (1.0.4)
     sass (3.4.13)
     sass-rails (5.0.1)
@@ -484,10 +461,6 @@ GEM
       unf_ext
     unf_ext (0.0.6)
     unicode-display_width (1.4.0)
-    unicorn (4.8.3)
-      kgio (~> 2.6)
-      rack
-      raindrops (~> 0.7)
     vcr (3.0.1)
     virtus (1.0.5)
       axiom-types (~> 0.1)
@@ -520,9 +493,6 @@ DEPENDENCIES
   axlsx_rails
   bootstrap-sass (>= 3.4.1)
   byebug
-  capistrano
-  capistrano-maintenance (= 0.0.5)
-  capistrano-sidekiq
   carrierwave
   chroma
   compass-rails (= 2.0.4)
@@ -570,7 +540,6 @@ DEPENDENCIES
   rolify
   rubocop (~> 0.61.1)
   rubyzip (>= 1.2.2)
-  rvm-capistrano
   sass-rails (= 5.0.1)
   sdoc (~> 0.4.0)
   seed_dump
@@ -586,7 +555,6 @@ DEPENDENCIES
   twitter
   twitter-text
   uglifier (>= 4.1.20)
-  unicorn
   vcr
   web-console (~> 2.1.3)
   webmock