added forget method to remove the data from session

[siddiquipro]

Added a forget method to remove the key from the session data.
we can rename the method to something else as well.

[jcs224]

Thanks for the PR! This would be a good feature to have!

Any chance you could also incorporate this feature into the browser test? Otherwise, I'll get around to it eventually.

[siddiquipro]

I have updated the browser tests to accommodate forget method.