Adds bundle install after standard gem addition

Adds a bundle install run after the standard gem is added to the
Gemfile. Without the bundle install suspenders runs into the following
error when the gems are bundle into vendor/path by default:

"Could not find gem 'standard' in locally installed gems."

Author: sfroehler

lib/suspenders/generators/lint_generator.rb

@@ -2,12 +2,16 @@
 
 module Suspenders
   class LintGenerator < Generators::Base
+    def add_standard
+      gem "standard", group: :development
+      Bundler.with_unbundled_env { run "bundle install" }
+    end
+
     def set_up_hound
       copy_file "hound.yml", ".hound.yml"
     end
 
     def set_up_standard
-      gem "standard", group: :development
       prepend_to_file("Rakefile", 'require "standard/rake"')
     end
   end

spec/suspenders/generators/lint_generator_spec.rb

@@ -8,6 +8,7 @@
 
         expect("Gemfile")
           .to match_contents(/gem .standard./)
+          .and have_bundled("install")
           .and have_no_syntax_error
       end
     end