Add tests for Proxy

Use the more common array syntax for includes

Fix monkey yaml's handling of carriage return

monkeyYaml didn't split lines correctly leading to \r in resulting
values.

Fixes #295

Insert omitted `negative` tag

Remove `$FAIL` function

This test exercises an early error, so it should be declared with the
`negative` tag.

This function is equivalent to `$ERROR` (which is automatically included
in test environments). Remove the harness file that defines the
function, remove references to the file from test `includes` lists, and
update scripts to instead invoke the `$ERROR` function.

Fixed testing deletion of an environment object.

Remove remaining includes for `assert.js` helper

No need to include asserts.js

The previous description of the 11.4.1-4.a-5 test case implied that an environment object could not be deleted while inside a with. However, the actual test was to test whether the variable declaration could be deleted. The description has been updated to better reflect this.

Add tests for early errors in module syntax

for..of additions

Generator test should specify generators feature.

Test 11.4.1-4.a-5 states that it verifies that an environment object cannot be deleted. However, this was giving a false positive. It was actually testing where a "var" declaration on an environment object cannot be deleted (there are other tests for this). This test case fails on Chrome 43, Firefox 38 and Internet Explorer 11.

Introduce the `module` flag to unambiguously identify tests that are
intended to be interpreted as module code.

Update contribution guidelines

- Remove trailing white space
- Streamline documentation of test tags
- Do not reference obsolete tags
- Document `features` frontmatter tag
- Document `es6id` frontmatter tag
- Omit unnecessary detail about test262 website generation. This is not
  directly useful to potential test contributors. Implementation details
  like these can be taken for granted by that audience.
- Remove documentation on YAML syntax. Details on YAML may be helpful
  for some new contributors, but this document should not attempt to
  cover the topic (especially not from the description of a specific
  frontmatter entry). Replace with a link to a more comprehensive source
  as this will be more generally useful to those who need it (and less
  obtrusive for those who do not).
- Consolidate information on test helpers
- Document `assert` helpers
- Update instructions for asserting errors. Since the introduction of
  `assert.throws` in gh-22, the preferred means of expressing
  expectations regarding errors has changed. Update the CONTRIBUTING.md
  file to reflect the latest approach. Explain purpose of `throw
  NotEarlyError;` in example test.
- Re-order information on file names. The inconsistency in the project's
  file names should not go unmentioned, but neither should it not
  preceed instructions for the accepted approach to namine tests.
- More clearly document required frontmatter tags. Explicitly list
  `description` as a required frontmatter tag, implicitly identifying
  all other tags as optional.

Add tests for destructuring assignment