Check if connection is open on sendPing & change readystate on closeConnection

[marci4]

Description

Check in the timertask to make sure that a connection is really open.
closeConnection() can also adjust the readystate to closing, if the closecode is CloseFrame.Abnormal_Close and the connection is still open

Related Issue

#606
Fixes #609

Motivation and Context

#606 caused an exception
#609 just looked messy. But was no real problem due to closeConnection() changing the readystate to closed at the end

How Has This Been Tested?

Tested against demo project. Waiting for user feedback

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.