Fix timing issue with electron@8

[steveetm]

Fix issue #64
ipc.connect() is an async function, I don't really know why it is working with electron@7, but it is definitely not a good idea to expect client to be ready to send messages without waiting connec()

[mrfelton]

Tested ACK

[veado]

Have checked that ^ in a project running on Electron 8.x - it works great! Thx @steveetm for this fix!

[AndreyBelym]

Thank you for your contribution. In the older (>5.0.0) Electron version there was no documentation on the webContents.loadURL return type:
https://github.com/electron/electron/blob/v4.2.12/docs/api/web-contents.md.

Since it was unclear if this function has some synchronous side effects, I purposely tried to keep the loadURL mock synchronous to avoid breaking the user's app behavior.

If we want to make loadURL asynchronous, I will need some time to check if it works in the older Electron versions and doesn't introduce unwanted side effects.

[veado]

If we want to make loadURL asynchronous, I will need some time to check if it works in the older Electron versions and doesn't introduce unwanted side effects.

@AndreyBelym How about to stick on v0.0.15-alpha.1 or < v0.0.14 for using older Electron versions ^, but not blocking this PR?

[AlexKamaev]

@veado
We do not block this PR. We just need time to research it deeply.