Removed es5 killer script for development testing as it makes ruins the browser runner
Make the standard assertion error available without throwing
Fixing jshint errors
Lint test files
Handle nested expects inside of custom assertion in a more controlled
manner

Changes the default handling of nested expects inside assertions to use
the standard error message for the assertion instead of the error
message of the nested expect.

Two new boolean flags has been added to the assertion in order to
control how error messages of nested expects are handled.

* bubbleExpectErrors: use the error message of the nested expect
* nestExpectErrors: show the standard error for the assertion followed
  by the error message of the nested expect.

Example of the default behaviour:

```js
expect.addAssertion('to be a number with value', function (value) {
    expect(this.obj, 'to be a number');
    expect(this.obj, 'to be', value);
});
expect('42', 'to be a number with value', 42);

// throw: expected '42' to be a number with value 42
```

Example of bubbleExpectErrors:

```js
expect.addAssertion('to be a number with value', function (value) {
    this.bubbleExpectErrors = true;
    expect(this.obj, 'to be a number');
    expect(this.obj, 'to be', value);
});
expect('42', 'to be a number with value', 42);

// throw: expected '42' to be a number
```

Example of nestExpectErrors:

```js
expect.addAssertion('to be a number with value', function (value) {
    this.nestExpectErrors = true;
    expect(this.obj, 'to be a number');
    expect(this.obj, 'to be', value);
});
expect('42', 'to be a number with value', 42);

// throw: expected '42' to be a number with value 42
              expected '42' to be a number
```

This works recursively of cause.

------------------------------------------------------------------

After doing this change I need to fix the output of some of the
assertions and change the test to expect the improved error messages.
Fixed stupid spelling error
Fixed resetting the wrong variable
Use a single flag to control error messages instead of two
Handle nesting of custom async assertions by wrapping expect
Added this.obj back as deprecated
Fixed spelling error
Fixed truncation of the stack for _wrappedExpect and fixed #29.

I added 2 tests, but I couldn't get one of them to pass using mocha-phantomjs, so I eventually gave up and marked it as pending.
Added grep parameter to test target
Give the expect functions names to improve stack truncation
Skip stack truncation in phantom
Test error modes for asynchronous custom assertions
Fixing jshint errors
Fixed failing test after rebase
Rebased on master
Documenting how to extend Unexpected.