Code: Mics. formattings

Feature: Configurable linefeed and indent

* `indentType` can be space or tab.
  * default: space.
* `indentWidth` is a positive integer.
  * default: 2.
  * maximum: 10
* `linefeed` could be:
  * cr
  * crlf
  * lf
  * lfcr

Issue URL: #682.
PR URL: #792.

malloc() needs <stdlib.h>

Custom functions

Submodule: Updates LibSass to v3.2.0-beta.1

* Updates sass-spec to corresponding commit.
* Prevents source_string from freeing in
  data context case in binding code.
  * Corresponds to sass/libsass#925.

Code: Parses arguments manually

Build with the unbundled libsass

Use environment variables to control
how libsass is linked:

LIBSASS_EXT variable empty or unset

Build a bundled libsass source
(from src/libsass).
This is the default.

LIBSASS_EXT=auto

libsass is located using pkg-config
and linked dynamically

LIBSASS_EXT=yes
LIBSASS_CFLAGS=    compiler flags
LIBSASS_LDFLAGS=   linker flags
LIBSASS_LIBRARY=   library to link

Link libsass manually, by adding
compiler and linker flags.

For example this way libsass can
be linked in statically (on Unix):

LIBSASS_EXT=yes
LIBSASS_CFLAGS=-I/usr/local/include
LIBSASS_LIBRARY=/usr/local/lib/libsass.a

When using LIBSASS_EXT there is no need
to checkout the libsass source into src/libsass submodule
and the library from the package management
system can be used.

PR: #139
PR: #389
PR: #744

Issue URL: #769.
PR URL: #770.

CLI: Do not require input file on watch

* Removes input file parameter from watch test.
* Uses `once` instead of `on` in CLI tests.
  * Removes `bin.kill` in favour of `once`.

Issue URL: #755.
PR URL: #761.

Repo: Adds .gitattributes

Issue URL: #758.
PR URL: #760.

Code: Minor formatting

Install: Fixes download bug 🐛

PR URL: #743.

* Pointed out by @saper via #694.

PR URL: #743.

* Delivers binary name, paths and download URL
  from lib/extensions.js.

* Allows user to set binary name as environment
  variable with `SASS_BINARY_NAME`.
  * Note: this will supersede default name.
* Allows user to set binary name as in package
  file `"nodeSassConfig": { "binary-name": "" }`.
  * Note: this will supersede default name and
    `SASS_BINARY_NAME` environment variable.
* Allows user to set binary name as parameter to
  invoke any node-sass script with
  `--binary-name` flag.
  * Note: this will supersede default name, name
    defined in package `nodeSassConfig` as well
    as the `SASS_BINARY_NAME` environment
    variable.

* This binary name will be used to construct the:
  * Binary path.
  * Binary download URL.
  * Upload URL.

* Allows user to set binary path as environment
  variable with `SASS_BINARY_PATH`.
  * Note: this will supersede default path.
* Allows user to set binary name as in package
  file `"nodeSassConfig": { "binary-path": "" }`.
  * Note: this will supersede default path and
    `SASS_BINARY_PATH` environment variable.
* Allows user to set binary path as parameter to
  invoke any node-sass script with
  `--binary-path` flag.
  * Note: this will supersede default path, path
    as well as the `SASS_BINARY_PATH` environment
    variable.

* This binary path will be used when:
  * Requiring node-sass package.
  * Downloading binary.
  * Uploading binary.

* Wraps all extensions in `process.sass`
  namespace.

Issue URL: #712.
PR URL: #743.

Issue URL: #731.
Pull Request: #732.

* CSS and Map is casted as Buffer from binding.
Advantages:
  * Buffers are super fast.
  * User can write them to file as is.
  * User can forward to response stream as is.
  * User can strigify it as is:
    * `result.css.toString()`
    * `result.map.toString()` or
      `JSON.stringify(result.map)`
* Updates tests and CLI usage accordingly.
* Updates README to reflect the changes.

Issue URL: #711.
PR URL: #729.

Better default values in the README.md file

This improves the option documentation for #672 and adds the default
information gleaned from the `getOptions` functions and their defaults
from the prior README.md