Use .ruby-version to detect our Ruby version

Travis and Rubocop and rmv1-capistrano3 automatically detect the version
based on the `.ruby-version` file.

.rubocop_basic.yml

@@ -9,7 +9,6 @@ AllCops:
   Exclude:
     - "db/migrate/**/*"
     - "db/schema.rb"
-  TargetRubyVersion: 2.3
   # RuboCop has a bunch of cops enabled by default. This setting tells RuboCop
   # to ignore them, so only the ones explicitly set in this file are enabled.
   DisabledByDefault: true

.travis.yml

@@ -2,8 +2,6 @@ language: ruby
 addons:
   postgresql: "9.4"
   chrome: stable
-rvm:
-- 2.3.2
 cache: bundler
 bundler_args: --without development
 before_script:

config/deploy.rb

@@ -7,7 +7,6 @@ def deploysecret(key)
 end
 
 set :rails_env, fetch(:stage)
-set :rvm1_ruby_version, "2.3.2"
 set :rvm1_map_bins, -> { fetch(:rvm_map_bins).to_a.concat(%w[rake gem bundle ruby]).uniq }
 
 set :application, "consul"
@@ -63,9 +62,11 @@ end
 
 task :install_bundler_gem do
   on roles(:app) do
+    within release_path do
       execute "rvm use #{fetch(:rvm1_ruby_version)}; gem install bundler"
     end
   end
+end
 
 task :refresh_sitemap do
   on roles(:app) do