Measure coverage for all js tests

Instrument spec.js for test coverage
measurement.

Instrument all .js files in the test
directory.

.jshintignore

@@ -1 +1,2 @@
 node_modules/**
+test/coverage/html

scripts/coverage.js

@@ -56,7 +56,7 @@ function coverage() {
                  instrumentedfiles.push(source);
                  if (instrumentedfiles.length === sourcefiles.length) {
                    fs.readdirSync('test').filter(function(file){
-                     return file.substr(-6) === 'api.js';
+                     return file.substr(-3) === '.js';
                    }).forEach(function(file){
                      mocha.addFile(
                        path.join('test', file)

test/spec.js

@@ -3,7 +3,9 @@ var assert = require('assert'),
     exists = fs.existsSync,
     path = require('path'),
     read = fs.readFileSync,
-    sass = require('../lib'),
+    sass = process.env.NODESASS_COV
+      ? require('../lib-cov')
+      : require('../lib'),
     util = require('./util');
 
 describe('spec', function() {