replace imports of q with bluebird

update `package.json`

```
find src test -name '*.js' |
    xargs perl -i -pe 'if (/require\(.[qQ].\)/) { $_ = "import Promise from '\''bluebird'\'';\n"; }'

find src test -name '*.js' |
    xargs perl -i -pe 'if (/import [qQ] /) { $_ = "import Promise from '\''bluebird'\'';\n"; }'
```

test/app-tests/joining.js

@@ -33,7 +33,7 @@ var React = require('react');
 var ReactDOM = require('react-dom');
 var ReactTestUtils = require('react-addons-test-utils');
 var expect = require('expect');
-var q = require('q');
+import Promise from 'bluebird';
 
 var test_utils = require('../test-utils');
 var MockHttpBackend = require('matrix-mock-request');