11/13 tests fail on ruby 2.0p247

```
sevenspaces-3:~ corprew$ mkdir demo
sevenspaces-3:~ corprew$ cd demo
sevenspaces-3:demo corprew$ git clone https://github.com/Mashape/unirest-ruby.git
Cloning into 'unirest-ruby'...
remote: Counting objects: 489, done.
remote: Total 489 (delta 0), reused 0 (delta 0)
Receiving objects: 100% (489/489), 87.12 KiB | 0 bytes/s, done.
Resolving deltas: 100% (210/210), done.
Checking connectivity... done.
sevenspaces-3:demo corprew$ cd unirest-ruby
sevenspaces-3:unirest-ruby (master)corprew$ rake test
/Users/corprew/.rvm/rubies/ruby-2.0.0-p247/bin/ruby -I"lib:test" -I"/Users/corprew/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib" "/Users/corprew/.rvm/gems/ruby-2.0.0-p247/gems/rake-10.4.2/lib/rake/rake_test_loader.rb" "test/unirest_test.rb"
/Users/corprew/.rvm/gems/ruby-2.0.0-p247/gems/minitest-5.4.0/lib/minitest/assertions.rb:15: warning: already initialized constant MiniTest::Assertions::UNDEFINED
/Users/corprew/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/minitest/unit.rb:79: warning: previous definition of UNDEFINED was here
Run options:

# Running tests:

[ 1/13] Unirest::RequestsTest#test_: Unirest::Requests should Basic Authentication. = 0.28 s
1) Error:
test_: Unirest::Requests should Basic Authentication. (Unirest::RequestsTest):
NoMethodError: undefined method `assertions' for #
/Users/corprew/.rvm/rubies/ruby-2.0.0-p247/lib/ruby/2.0.0/test/unit/assertions.rb:38:in `assert'
/Users/corprew/demo/unirest-ruby/test/unirest_test.rb:129:in `block in '
/Users/corprew/.rvm/gems/ruby-2.0.0-p247/gems/shoulda-context-1.2.1/lib/shoulda/context/context.rb:413:in `instance_exec'
```

Run `rake test` on Ruby 2.0.0-p247 and inspect the failures in `test/unirest_test.rb`, beginning with the `Unirest::RequestsTest` Basic Authentication case and its `assertions` error. Done means the reported Ruby 2.0 test failures are resolved and the full test suite passes.

Written by the indexing model from the issue text.