Ignore scripts dir; Warn on non-doc first lines

[ZoomRmc]

This PR fixes the directory.nim:

• The scripts directory is now ignored.
• When a program tries to read the algorithm's title from the first line of source code, it now warns if this line is not a doc comment.
• Usage is clarified a bit.

I can modify the guidelines now to require this for updating the directory.md file.

[dlesnoff]

I would like a modification of the guidelines (contributing.md) to specify the need to update the directory.md file with the script and I will merge this. Thanks !

[ZoomRmc]

I've started working on the guidelines, but I would like to propose some additional changes so it will require a separate PR.

[dlesnoff]

Fine by me!