Gemfile: remove unused gems.

coffee-rails and daemons are unused.

kgio, net-ssh, and nokogiri are pulled in by other gems, but they aren't
used by us directly, so they shouldn't need to be listed in the Gemfile.

Gemfile.lock

@@ -106,16 +106,8 @@ GEM
     chronic (0.10.2)
     cityhash (0.8.1)
     coderay (1.1.1)
-    coffee-rails (4.1.0)
-      coffee-script (>= 2.2.0)
-      railties (>= 4.0.0, < 5.0)
-    coffee-script (2.4.1)
-      coffee-script-source
-      execjs
-    coffee-script-source (1.9.1.1)
     colorize (0.7.7)
     crass (1.0.2)
-    daemons (1.2.3)
     dalli (2.7.4)
     delayed_job (4.0.6)
       activesupport (>= 3.0, < 5.0)
@@ -387,8 +379,6 @@ DEPENDENCIES
   capistrano-rbenv
   capistrano3-unicorn
   cityhash
-  coffee-rails
-  daemons
   dalli
   delayed_job
   delayed_job_active_record
@@ -401,16 +391,13 @@ DEPENDENCIES
   gctools
   google-api-client
   highline
-  kgio
   mechanize
   memcache-client
   memcache_mock
   memoist
   mocha
   net-sftp
-  net-ssh
   newrelic_rpm
-  nokogiri
   pg
   protected_attributes
   pry