Add make target to run karma tests with auto-watch enabled

This provides a convenient way to start Karma tests and auto-run
them when test files are changed.

Because the test files are incorporated into a Browserify bundle
by karma-browserify which watches files for changes via watchify(),
we can turn off Karma's own watching of the test files.

This fixes a problem where changing a test spec file would result
in Karma running all the tests twice, once after the test spec file
changed and then again afterwards due to the browserify bundle
being updated a second or two after the test spec file changes.

h/static/scripts/karma.config.js

@@ -38,8 +38,12 @@ module.exports = function(config) {
       'test/bootstrap.js',
 
       // Tests
-      '**/*-test.coffee',
-      '**/*-test.js'
+      //
+      // Karma watching is disabled for these files because they are
+      // bundled with karma-browserify which handles watching itself via
+      // watchify
+      { pattern: '**/*-test.coffee', watched: false, included: true, served: true },
+      { pattern: '**/*-test.js', watched: false, included: true, served: true }
     ],
 
     // list of files to exclude

package.json

@@ -45,7 +45,7 @@
   "devDependencies": {
     "chai": "^3.2.0",
     "jscs": "^1.13.1",
-    "karma": "^0.12.17",
+    "karma": "^0.13.10",
     "karma-browserify": "^3.0.3",
     "karma-chai": "^0.1.0",
     "karma-cli": "0.0.4",