Drop support for Travis CI (#208)

This removes all references, including the config file, documentation
and CLI helper we have.

README.md

@@ -1,13 +1,8 @@
 Appraisal
 =========
 
-[![Build Status][Build Status Image]][Build Status]
-
 Find out what your Ruby gems are worth.
 
-[Build Status Image]: https://secure.travis-ci.org/thoughtbot/appraisal.svg?branch=master
-[Build Status]: http://travis-ci.org/thoughtbot/appraisal
-
 Synopsis
 --------
 
@@ -89,7 +84,7 @@ your real default task, which usually is your `test` task.)
 
 Note that this may conflict with your CI setup if you decide to split the test
 into multiple processes by Appraisal and you are using `rake` to run tests by
-default. Please see **Travis CI Integration** for more detail.
+default.
 
 ### Commands
 
@@ -201,35 +196,7 @@ Version Control
 When using Appraisal, we recommend you check in the Gemfiles that Appraisal
 generates within the gemfiles directory, but exclude the lockfiles there
 (`*.gemfile.lock`.) The Gemfiles are useful when running your tests against a
-continuous integration server such as [Travis CI][Travis CI].
-
-[Travis CI]: https://travis-ci.org
-
-Travis CI integration
----------------------
-
-If you're using Appraisal and using Travis CI, we're recommending you to setup
-Travis to run the test against multiple generated Gemfiles. This can be done
-by using `gemfile` setting:
-
-    # In .travis.yml
-    gemfile:
-      - gemfiles/3.0.gemfile
-      - gemfiles/3.1.gemfile
-      - gemfiles/3.2.gemfile
-
-Please note that if you've set your default rake task to run the test against
-all versions of its dependency, you might have to set a `script` setting:
-
-    script: "bundle exec rake test"
-
-That will make sure that each of the test sub-job are not getting run more than
-one time.
-
-You can also run your tests against multiple versions of Ruby locally, just
-like running on Travis CI, by using [WWTD].
-
-[WWTD]: https://github.com/grosser/wwtd
+continuous integration server.
 
 Circle CI Integration
 ---------------------

lib/appraisal/cli.rb

@@ -1,6 +1,5 @@
 require 'thor'
 require 'fileutils'
-require "appraisal/travis_ci_helper"
 
 module Appraisal
   class CLI < Thor
@@ -63,17 +62,10 @@ def install
     end
 
     desc 'generate', 'Generate a gemfile for each appraisal'
-    method_option "travis", :type => :boolean, :default => false
     def generate
       AppraisalFile.each do |appraisal|
         appraisal.write_gemfile
       end
-
-      if options[:travis]
-        TravisCIHelper.display_instruction
-      else
-        TravisCIHelper.validate_configuration_file
-      end
     end
 
     desc 'clean', 'Remove all generated gemfiles and lockfiles from gemfiles folder'