This commit fixes serving of newly added files

This commit handles the issue in serve command which cannot host
new files. It is worth noting that new file content won't appear
until the tags are added.

Fixed #19
No `camelCase` please. Use one of:

* `HolocronHandler` to point that it's a class object
* `holocron_handler` to point that it's a variable

I can't suggest what to use here. Perhaps second variant.. because I don't see the first one in the world.