Minimal updates to pure Python kernel to keep it (somewhat) API compatible with the IPython Kernel. We should define a basic interface for Kernel objects so that we do not continue to have these problems.

Implemented kernel interrupts for Windows.

Fixed inconsistent usage of has_kernel in KernelManager.

Fixing problem with first_reply signal.

Added a first_reply signal to the heartbeat channel.

Added pausing to the heartbeat channel.

Removed use of hard tabs in FrontendWidget and implemented "smart" backspace.

Pressing Enter now always executes when the input buffer has one line.

Fixing typo in ipkernel.py

New connect_request message type added.