Increase the version of libtorrent in our build script

[devos50]

Our build script currently builds libtorrent 1.2.1, a version that is already a few years old. We should increase this version to include the stability fixes/performance improvements made to the libtorrent code base.

Around version 1.2.11, the process to build the libtorrent Python bindings have changed a bit since it now uses setuptools. I still haven't figured out how to build it exactly, but the current make command we have in our build script is not working properly. This is something we need to check out.