Read multiple-characters keys only when stdin is not empty

[MatteoCampinoti94]

The first character is read normaly, subsequent reads are done with NONBLOCK flag active allowing for special characters 0x1b 0x5b 0x33 to be read alone without having to wait for a second read. This for example allows to use readkey to detect a single press of ESC which would have otherwise not returned anything until a second key was pressed that was different than x05b. With the old behavior presssing ESC and then a cursor key would have returned '0x1b0x1b' leaving two characters still stored in the buffer on top of providing an incorrect read.

Old behavior was conserved to allow for getchar_fn to keep functioning properly

All tests provided were passed

[MatteoCampinoti94]

requirements.txt is missing thus failing all automated tests on travis-ci. Skipping the pip command allows for proper testing as the makefile works perfectly.

[MatteoCampinoti94]

It's not just the requirements file missing, the command pip freeze -a fails tooo because -a is not an option. Furthermore python setup.py install doesn't seem to work either in the automated test environment (it works fine with python 3.x on my machine)

[Cube707]

out of date