Map f1-f4 escape codes used in rxvt-unicode
Map f1-f4 escape codes used in rxvt-unicode

Fixes https://github.com/jonathanslenders/python-prompt-toolkit/issues/83

jaseg/python-prompt-toolkit,amjith/python-prompt-toolkit,jonathanslenders/python-prompt-toolkit,melund/python-prompt-toolkit,ALSchwalm/python-prompt-toolkit,ddalex/python-prompt-toolkit,niklasf/python-prompt-toolkit