Enable users to inform a custom templates path at runtime

[pantuza]

This Pull Request solves #6 . It has the following contributions:

1. Adds a new command line option: -t | --templates-path that will be then used as the path for reading templates.
2. Updates Sphinx version and rebuild project documentation
3. Fixes a broken test

How to test

Follow the steps described in this documentation.
Instead of creating the templates path on the current directory, try creating elsewhere. For example: /tmp/templates/.
Thus, when you call the CLI, inform the command argument: -t /tmp/templates.
If omitted, it must default to templates/ in the current directory.

[pantuza]

I see this PR has changed 24 files. Sorry for that! It turns out only 3 files were actually modified by me.
The other files were auto generated by building project documentation using Makefile.