`rake` and `rake test` fails

Running `rake` or `rake test` fails with the following (with and without `bundle exec`):

``` sh
➜ github-ldap git:(feature/multi_domain) rake
/Users/davesims/github/github-ldap/test/test_helper.rb:20:in `': undefined method `after_run' for MiniTest:Module (NoMethodError)
from /Users/davesims/github/github-ldap/test/domain_test.rb:1:in `require_relative'
from /Users/davesims/github/github-ldap/test/domain_test.rb:1:in `'
from /Users/davesims/github/github/vendor/ruby/11323111113067d8fc579071c01d83e9f161adc4/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/davesims/github/github/vendor/ruby/11323111113067d8fc579071c01d83e9f161adc4/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb:10:in `block (2 levels) in '
from /Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb:9:in `each'
from /Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb:9:in `block in '
from /Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb:4:in `select'
from /Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb:4:in `'
rake aborted!
Command failed with status (1): [ruby -I"lib:test" -I"/Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib" "/Users/davesims/github/github/vendor/gems/2.1.7/bundler/../ruby/2.1.0/gems/rake-10.5.0/lib/rake/rake_test_loader.rb" "test/**/*_test.rb" ]

Tasks: TOP => default => test
(See full trace by running task with --trace)
```

Workaround is to run test files directly through ruby & bundler

``` sh
➜ github-ldap git:(feature/multi_domain) bundle exec ruby -Ilib:test test/**/*_test.rb
Run options: --seed 6062

# Running:

....................................................

Finished in 3.112345s, 16.7077 runs/s, 23.4550 assertions/s.

52 runs, 73 assertions, 0 failures, 0 errors, 0 skips
```

从 test/test_helper.rb:20 开始，MiniTest.after_run 会在此处引发报告中的错误，然后运行 rake 和 rake test 来复现该错误。将这些结果与 issue 中显示的直接 ruby 测试命令进行比较；当两个 Rake 命令都成功完成且测试套件通过时，即表示完成。

由索引模型根据 Issue 内容生成。