use entry_points for setting up bin script

[MasterOdin]

Gets rid of the symlinked tldr that was getting installed as a script (to make doing tldr work) and use entry_points / console_scripts instead which is the proper way. This also means that someone cloning the repo on Windows will not have a useless file.

[MasterOdin]

For future reference to anyone interested, the entry_points was added back when this project started, but was then removed in da8c106 due to the cited reason of "Don't use entry points, they are too slow". The historical reference for this would be that back then, doing python3 setup.py install was a recommended way of doing things (and maybe also pip) which would wrap the script in a pkg_resources reference. Importing pkg_resources could add a lot of overhead on running a script (see pypa/setuptools#711 for discussion on it). However, since then, python3 setup.py install has become a deprecated way of installing things, preferring to do pip3 install ., which bypasses pkg_resources and keeps running the script snappy, without having to resort to workarounds.