TestCase: Close session in tearDown.

Before this fix it worked only if there was no other reference to the session object, in that case the destructor was called and session stopped.
Removed unnecessary return from __set().
Formatting fixes.
BrowserSession::waitForAlert: Fixed return docblock tag.

FALSE is not a type, bool is.
typos
Composer.json: Removed version.

It's better to keep this information in Git tags or branches.