Add simple test for exports

test/all.js

@@ -1,4 +1,7 @@
 
+// Module API
+require('./exports');
+
 // Utilities
 require('./location');
 require('./paths');

test/exports.js

@@ -0,0 +1,12 @@
+var should = require('should');
+var gitbook = require('../');
+
+describe('Exports', function() {
+    it('should export the Book class', function() {
+        should(gitbook.Book).be.a.Function();
+    });
+
+    it('should export the list of commands', function() {
+        should(gitbook.commands).be.an.Array();
+    });
+});