Advice for creating a web app

[Jumping until blue]

I'm confused ... and need some advice

Here is what I want to do:

I have a number of files, mostly text files formatted using Markdown
syntax but also pdfs and other types of files, that are stored in a
folder hierarchy and I want to develop a web application where I can
brows, view and search these files. The documents can be
cross-linked.

Currently I use a basic CGI to view/format the markdown files but I
don't know if I should continue to make my own system or if I should
take advantage of some existing framework.

My requirements are:

+   It should work with the text files I have in my
    hierarchy (so a system that stores everything
    in a database is out of the question)

+   I want to be able to copy the folder hierarchy
    to a memory stick and run my system on another
    computer without having to install any software
    (I'm thinking of using something like Movable 
    Python). I'll mostly be running this on Macs
    but would like to have the option to run it
    on Windows/Linux

+   Searching should be fairly fast

+   I should be able to edit the text files using a
    standard text editor without messing up the system.

+   I will use subversion to keep different computers
    in sync.

So my question is: should I use some existing framwork? and if so,
which ones should I look at? TurboGears, Django, etc seem to be much
too elaborate for my modest needs.