Python 2 fix (string.isidentifier did not yet exist.)
Implemented something to use a 'cursor position request' for calculating the first initial height of the 'ptpython' prompt.
Fixed bug in _cpr_response_prefix_re
Also request_absolute_cursor_position after Ctrl-C key press.
Merge pull request #4 from amjith/master

Fix C-w and C-u in the insert mode.
Don't insert control sequences in input stream. (We have quoted insert.)