update README.md with build instructions

README.md

@@ -10,3 +10,15 @@ WARNING: Modify settings at your own risk!
 
 For information about each setting, see the libtorrent [manual](http://www.rasterbar.com/products/libtorrent/manual.html#session-customization).
 NOTE: Older versions of libtorrent may have different setting names.
+
+Building
+--------
+
+To build this plugin, you'll need [Python](https://www.python.org/) and the `setuptools` module. Instructions for installing `setuptools` can be found [here](https://packaging.python.org/tutorials/installing-packages/#install-pip-setuptools-and-wheel).
+
+To build the plugin, run:
+```
+python setup.py bdist_egg
+```
+
+This will produce a `dist` directory containing the plugin egg.