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"; }'
```

src/ContentMessages.js

@@ -16,7 +16,7 @@ limitations under the License.
 
 'use strict';
 
-var q = require('q');
+import Promise from 'bluebird';
 var extend = require('./extend');
 var dis = require('./dispatcher');
 var MatrixClientPeg = require('./MatrixClientPeg');