Introduced .npmrc variables to configure sass binary parameters

lib/extensions.js

@@ -48,7 +48,8 @@ function getRuntimeInfo() {
 
 /**
  * Get binary name.
- * If environment variable SASS_BINARY_NAME or
+ * If environment variable SASS_BINARY_NAME,
+ * .npmrc variable sass_binary_name or
  * process argument --binary-name is provided,
  * return it as is, otherwise make default binary
  * name: {platform}-{arch}-{v8 version}.node
@@ -63,6 +64,8 @@ function getBinaryName() {
     binaryName = flags['--sass-binary-name'];
   } else if (process.env.SASS_BINARY_NAME) {
     binaryName = process.env.SASS_BINARY_NAME;
+  } else if (process.env.npm_config_sass_binary_name) {
+    binaryName = process.env.npm_config_sass_binary_name;
   } else if (pkg.nodeSassConfig && pkg.nodeSassConfig.binaryName) {
     binaryName = pkg.nodeSassConfig.binaryName;
   } else {
@@ -80,7 +83,8 @@ function getBinaryName() {
  * site on GitHub.
  *
  * The default URL can be overriden using
- * the environment variable SASS_BINARY_SITE
+ * the environment variable SASS_BINARY_SITE,
+* .npmrc variable sass_binary_site or
  * or a command line option --sass-binary-site:
  *
  *   node scripts/install.js --sass-binary-site http://example.com/
@@ -104,6 +108,7 @@ function getBinaryName() {
 function getBinaryUrl() {
   var site = flags['--sass-binary-site'] ||
              process.env.SASS_BINARY_SITE  ||
+             process.env.npm_config_sass_binary_site ||
              (pkg.nodeSassConfig && pkg.nodeSassConfig.binarySite) ||
              'https://github.com/sass/node-sass/releases/download';
 
@@ -121,7 +126,8 @@ sass.runtime = getRuntimeInfo();
 
 /**
  * Get binary path.
- * If environment variable SASS_BINARY_PATH or
+ * If environment variable SASS_BINARY_PATH,
+ * .npmrc variable sass_binary_path or
  * process argument --sass-binary-path is provided,
  * select it by appending binary name, otherwise
  * make default binary path using binary name.
@@ -140,6 +146,8 @@ sass.getBinaryPath = function(throwIfNotExists) {
     binaryPath = flags['--sass-binary-path'];
   } else if (process.env.SASS_BINARY_PATH) {
     binaryPath = process.env.SASS_BINARY_PATH;
+  } else if (process.env.npm_config_sass_binary_path) {
+    binaryPath = process.env.npm_config_sass_binary_path;
   } else if (pkg.nodeSassConfig && pkg.nodeSassConfig.binaryPath) {
     binaryPath = pkg.nodeSassConfig.binaryPath;
   } else {