rename executable to simply `weberizer`

I'm a stickler for good simple names and don't see why the executable
shouldn't be named simply `weberizer`. Only issue I see is that now
the filename is different from the final executable name, which can be
a bit confusing because you won't know that without reading the _oasis
file. But I still think this is better.
separate lib and app files into separate directories

Actually, main point of this was to let the executable filename be
`weberizer.ml` by putting it in a separate directory from the
Weberizer module implementation, but I'm unable to make that work. I
get a circular build error. I don't see why this shouldn't work. For
now the file is still called `weberizer_compile.ml`.
Merge pull request #5 from agarwal/master

Makefile: improve reinstall command
Merge pull request #4 from agarwal/app-name

change app name to simply `weberizer`
Use oasis dynamic update.
Version 0.7.2
Update description.
Update to oasis 0.3.
Fix "tar" Makefile target.
Include the exception raised by bindings in error messages.
Simple caching system.
Generate a setup.ml independent of oasis for tarballs.
Add the possibility to cache when the program exits.
Ignore tarballs.
Add the function "key" to retrieve the key of a cache.
Improve function Cache.time.
Cache: avoid possible dependency cycles when updating.
Automatically escape spaces in emails (when protecting them).
Increase version.
Weberizer tarball independent of oasis.

Make a new release to drop the oasis dependency in OPAM.