::construct() methods may return NULL and
indicate an error in the returned error value.

This method uses Sass error value
as a vehicle to report the error message,
but returns NULL to indicate constructor
failure.

This is used to tell successful creation
of the Sass error object from the constructor
failure, where no valid Sass object can be
created.

Make the build process output actually
useful.

Update to the new Travis CI infrastructure.

http://docs.travis-ci.com/user/migrating-from-legacy/#Why-migrate-to-container-based-infrastructure%3F

Update reference of 'multi-file' to 'directory'

Standardise on cross-spawn for spawning child processes

The multi-file terminology is unintuitive and could be seen as
suggesting we support multiple input files, when in fact we're
describing directory support.

Empty data string is not a file name

There a known issues with `spawn` on Windows i.e. joyent/node#2318.
As a work around we sometimes use
[cross-spawn](https://www.npmjs.com/package/cross-spawn). We will
move all usage of `spawn` to `cross-spawn`.
Closes #1015.

Revert "Workaround the segfault that occurs when used with fsevents"

This reverts commit 3166b613.

Ensure we have nan@^2.0.8

This is to make sure binaries affected by
https://github.com/sass/node-sass/issues/1107 are never built

Remove C++11 feature in order to be
able to compile against libstdc++.so.6.0.9
on MacOSX.

Allow to link the binding against
oldish libstdc++.6.0.9 installed on MacOSX
(from gcc 4.2.1)

Workaround the segfault that occurs when used with fsevents

fsevents@0.3.8 introduces a segfault that manifests when used with
node-sass. fsevents is widely popular. As a mitigation we've added
fsevents@0.3.7 as an optionalDependency.The intention here is the
prevent users install node-sass@3.3.x and fsevents@0.3.8 by using
npm's deduping behaviour.

Intended to fix https://github.com/sass/node-sass/issues/924

node-gyp is using process.config.target_defaults.default_configuration
to check which configuration is about to be used, but this
can be overriden by particular engine's config.gypi file.

Since we do not support such a cross compilation anyway,
use this variable in place of a hardcoded default.

Instead of introducing another option to force the use
of 'Release' we should read and pass options to node-gyp.
This is not implemented here.

To speed up a build and avoid bombarding
nodejs.org and iojs.org with connections we should
cache what we download via npm and node-gyp.

CI: Adds explicit runtime versions in job matrix

* The artifact will be available under job details in `Artifacts` tab.
* URL format: `https://ci.appveyor.com/project/sass/node-sass/build/<build-id>/job/<job-id>/artifacts`.

Updates appveyor.yml.

Related: #1096

Be explicit about which runtime versions travis should test

Use new libsass GitHub link