The String.endsWith and String.includes tests didn't specify either an es6id or a features. Added a features attribute for these tests.

Some tests specifically concern the application of the `use strict`
directive as it appears in JavaScript source code. These tests should
*not* be run with the `onlyStrict` flag because relying on the test
runner to enable strict mode makes the semantics of the source code
irrelevant. Update these tests to use the `noStrict` flag.

Other tests concern language semantics that are only valid in strict
mode, but the mechanism for enabling strictness is inconseqential.
Update these tests to use the `onlyStrict` flag and remove any redundant
`use strict` directive prologues contained within.

Still other tests are valid both within and outside of strict mode.
In keeping with the majority of other tests, do not specify any
restrictions on the environments in which these tests may be run.

The `$PRINT` helper function has no effect on test behavior. The
following tests use it to report assertion outcomes (and as a result
will fail silently):

- test/language/function-code/S10.2.1_A4_T2.js
- test/language/function-code/S10.2.1_A5.1_T1.js
- test/language/function-code/S10.2.1_A5.1_T2.js
- test/language/function-code/S10.2.1_A5.2_T1.js

Remove the function definition and all references within tests. Update
tests that use it as an error reporting mechanism to instead use an
appropriate `assert` helper function.

In neglecting to assert the type of error thrown (or that any error was
thrown at all), these tests cannot fail. Refactor the tests to use the
`assert.throws` helper method, which takes these details into
consideration.

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.

Define tests for intrinsic Iterators under the appropriate subdirectory
of `built-ins`.

- Remove no longer needed noStrict flags.
- Change tests to use propertyHelper.js for strict mode compatibility.
- Add tests for return value of `delete` operator, e.g. `delete Array.prototype === false`.
- Add non-writable tests for global NaN property.
- Split some tests to run in strict mode.
- Change tests with global `var length` declaration to use a different variable name for browser environments.
- Merge duplicated tests symbol-data-property-configurable-non-strict and symbol-data-property-configurable-strict.
- Merge duplicated tests symbol-data-property-writable-non-strict and symbol-data-property-writable-strict.
- (And a small change in propertyHelper to reduce code duplication in function call.)

- Add missing "var" declarations and noStrict flags
- Remove with-statements (minor change in behaviour - primitive vs wrapper lookup, but does not seem too important for these tests)

Part of issue #35.

These tests are derived from the following files within the Google V8
project:

    test/mjsunit/es6/typed-array-iterator.js
    test/mjsunit/es6/arguments-iterator.js
    test/mjsunit/es6/string-iterator.js
    test/mjsunit/es6/collection-iterator.js

These tests are derived from the following files within the Google V8 project:

	test/mjsunit/harmony/private.js

These tests are derived from the following files within the Google V8
project:

    test/mjsunit/es6/templates.js

Some of these tests include non-printable characters, causing git to
infer that they are binary files. Introduce a `.gitattributes` file to
configure git to consistently display the source text of all JavaScript
files.

Fixes #185
Fixes #186

v8 would fail this test, so it would be nice to have it