test($test): Rename zip to unzip for clarity. Add descriptive error message to

Added unit tests for unzip and added a user-friendly error message for unzip being unable to perform
its duties of extracting a project.json from the given input (zip).

lib/unzip.js

@@ -0,0 +1,22 @@
+var JSZip = require('jszip');
+
+/**
+ * Unpacks a zip
+ *
+ * @param {String} Input
+ *
+ * @return {Object}
+ */
+module.exports = function (input, callback) {
+    return JSZip.loadAsync(input)
+        .then(function (zip) {
+            return zip.file('project.json').async('string')
+                .then(function (project) {
+                    return callback(null, [project, zip]);
+                });
+        })
+        .catch(function(err) {
+            var msg = 'Failed to unzip and extract project.json, with error: ';
+            return callback(msg + JSON.stringify(err));
+        });
+};