Fix links between modules in HTML docs output

The relative path to the root directory was wrong.

Probably the code handling the ActiveState distribution case also needs
the same fix, but I can't test it and hence haven't included it in this
fix.

Signed-off-by: Michael Wild <themiwi@users.sourceforge.net>
Merge pull request #15 from themiwi/patches/fix-html-links

Fix links between modules in HTML docs output