Basic setup for tests...

Running `ruby tests/xctest.rb` will now show the following:

```
In file included from /tmp/IILinqTests.m:1:
./IILinq/IILinq.h:8:1: warning: treating #import as an import of module 'Foundation' [-Wauto-import]
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@import Foundation;
1 warning generated.
Tests
  PASS test_it_works (0.000s)
Executed 1 test, with 0 failures (0 unexpected) in 0.000 (0.001) seconds
```

`tests.m` unsurprisingly is the file that contains all the tests, it
uses XCTestCase.

`xctest.rb` contains RUBIES which will:

- `prepare!` (copy tests.m to `/tmp/IILinqTests.m`)
- `compile!` (compiles `/tmp/IILinqTests.m` to `/tmp/IILinqTests`)
- `test!`    (execute the newly build app)

The output from that app will be colored and stripped from things you
don't care about.
Using module to squash warning.
Testing first example
Removing semicolon before body...

`./IILinq/IILinq.m:59:138: warning: semicolon before method body is ignored [-Wsemicolon-before-method-body]`
Test for shorthand.
Tests for inject and enumerating.
Merge remote-tracking branch 'origin/pr/1'