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/VectorConferenceHandler.js

@@ -16,7 +16,7 @@ limitations under the License.
 
 "use strict";
 
-var q = require("q");
+import Promise from 'bluebird';
 var Matrix = require("matrix-js-sdk");
 var Room = Matrix.Room;
 var CallHandler = require('matrix-react-sdk/lib/CallHandler');