Fix redefinition of `lwan_t`.

Found by @millken (https://github.com/lpereira/lwan/pull/3).
Remove symtab_add()

symtab_push() adds all variable descriptors, so there's no need to expose a
one-liner to add a symbol to the table.
Plug memory leak in cache

The pruner job wasn't correctly marking entries as floating. Not sure how I
missed this one; I should really think of a way to add tests to this
project.
Add test suite

This requires Python 'requests' module[1] and uses the standard 'unittest'
module. It is a black box test suite: nothing is tested internally, only how
the server reacts given certain inputs.

It assumes lwan is built in the 'build' directory, and that
'build/files_root' points to 'files_root'.

[1] http://www.python-requests.org/en/latest/
Cleanup index.html

Remove itworks.png, as it was borrowed from some website which I forgot the
address.
Add a bunch of new tests
Update README.md

Directory indexes! We have it!
Move things around in freegeoip app
Mark _coro_swapcontext() as __attribute__((noinline))
Save hash value in entry

Compare hash value first, then call the key comparison function. This should
provide faster hash table lookups.

Code has been written by Lucas De Marchi <lucas.demarchi@intel.com> for
libkmod -- which lwan's hash table implementation heavely bases upon.  A
blog post detailing this is available here:
http://www.politreco.com/2013/09/optimizing-hash-table-with-kmod-as-testbed/
Make sure lwan didn't crash while testing
Fix some test expectations
Add malformed request tests
Test requests with multiple accept-encoding values
Make sure file server redirects /directory to /directory/

This was done before but got removed once the caching stuff got wired in.
Simplify _get_data_and_funcs() to reduce number of arguments
Refactor _mmap_serve() and _dirlist_serve()

Use a common function that does pretty much the same thing.
Remove unneeded #includes
While building directory list, skip over special files (!dir && !regular)
Reduce size of headers array in _redir_serve()

It was larger due to a refactoring.