Add Config File option for passed in options

Resolves sasstools#226

Author: Snugug

docs/options/config-file.md

@@ -0,0 +1,5 @@
+# Config File
+
+Option `config-file` will tell Sass Lint the path to a custom config file. `config-file` should be set to a path plus file name relative to where Sass Lint is being run from. If not included, Sass Lint will attempt to find the closest config file, or fall back to the default one.
+
+Config File will only be respected if passed in as an option directly, not if it is already in a config file.

lib/config.js

@@ -40,6 +40,10 @@ module.exports = function (options, configPath) {
 
   options = options ? options : {};
 
+  if (options.options && options.options['config-file']) {
+    configPath = options.options['config-file'];
+  }
+
   if (!configPath) {
     metaPath = findFile(false, 'package.json');
     meta = require(metaPath);

tests/config.js

@@ -60,6 +60,25 @@ describe('config', function () {
     done();
   });
 
+  it('should use a config file if one is provided', function (done) {
+    var conf = config({
+          'options': {
+            'config-file': 'tests/yml/.stylish-output.yml'
+          }
+        }),
+        merged = merge.recursive(defaults, fs.readFileSync(path.join(__dirname, 'yml', '.stylish-output.yml')));
+
+    equal(
+      conf,
+      merged,
+      {
+        'strict': true
+      }
+    );
+
+    done();
+  });
+
   it('should not merge rules when `merge-default-rules` is false', function (done) {
     var opts = options,
         conf,