* Unfortunately, modern versions of jupyter clients (e.g. notebook)
queue execution requests at the client (rather than letting the
kernel do so) breaking the asynchronous execution model in
IJavascript. Users can make up for the loss of this feature with
`$$.display(id)`.
* For the above reason, I have disabled the previous behaviour of
awaiting for promises in execution results. To reenable this
behaviour see the below options.
* Added option `$$.config.awaitExecution` to enable the previous
default behaviour of awaiting for promises in execution results.
* Added option `Session(nelConfig.awaitExecution)` with the same
purpose to help implement the flag `--await-execution` in
IJavascript.
* Fixed issue https://github.com/n-riesco/ijavascript/issues/230
that caused the corruption of Jupyter notebooks.
