replace q method calls with bluebird ones

```
find src spec -name '*.js' |
    xargs perl -i -pe 's/q\.(all|defer|reject|delay|try)\(/Promise.$1(/'
```

spec/unit/crypto/algorithms/megolm.spec.js

@@ -136,7 +136,7 @@ describe("MegolmDecryption", function() {
             megolmDecryption.shareKeysWithDevice(keyRequest);
 
             // it's asynchronous, so we have to wait a bit
-            return q.delay(1).then(() => {
+            return Promise.delay(1).then(() => {
                 // check that it called encryptMessageForDevice with
                 // appropriate args.
                 expect(mockOlmLib.encryptMessageForDevice.calls.length)