Clarify custom importers and functions are still experimental

Handle build script git operations in JS

Fix bug with join defaulting to comma separator

Init libSass submodule when npm installing via git url

CLI: Adds --quiet flag

Close #713 (handle->flags & UV_CLOSING) assertion failure

Admin: Promoting Michael Mifsud to project lead

It is not safe to delete uv_async_t object after
calling uv_close(). This object remains in the
closing queue and can be purged only in the final
callback.

Fix typo lenth->length

Addresses #697.

Fixed lint error which was causing tests to fail.

CLI: Adds support for multi-file compilation.

Code: Skips path.resolve when outFile is not set

Code: Don't throw from interim callback state

Lets the error propagate to libsass.

This goes against the concept of fast aborting,
but this way downstream user will not get a blunt
exception, but receive a well-formatted JSON
error.

Note: this exception from importer callback's
post-process handler cannot be captured by try-
catch.

The edit in binding.cpp is also required, because
those conditions will never get satisfied anyway.
Removed due to aforementioned reasons.

Importer: Throws error on invalid return type

Issue URL: #670.
PR URL: #833.

API: Provides support for array of importers

* In order to skip the importer, user must
  return `sass.types.NULL` (or the shorter
  alias `sass.NULL`).
* See the added test on usage.
* Backward compatible: part of me want still
  wants to make it non-backward compatible
  because:
  * We can: in major version v3.0.
  * It will keep the API clean.
  * It will keep the docs clear: type of
    `options.importers` is array of functions.
* Updates docs.

Issue URL: #821.
PR URL: #832.

* Also updates dependencies versions.

ad br so readme cli options differentiate

Build: Adding libsass.gyp in a separate dir

* Turned out it isn't a bug, it's a feature!
  * npm/npm#7780

* Because we tend to fix them, not ignore.

* Adds corresponding tests.

Issue URL: #651.
PR URL: #817.

CLI: Adds support for Custom Functions