added S3FS class for accessing Amazon S3
whoops, add *latest* version of s3fs
added RPCFS, which exposes a filesystem using XML-RPC
make open(path,"w") immediately create an empty file in S3FS/RPCFS
Make listdirs(hidden=True) the default uniformly.

This was the case for all but OSFS and ZipFS, and it meant that copydir()
would not copy hidden files.  If this default isn't desired, walk() needs
to grow a hidden=True argument and copydir() needs to use it.
copydir:  don't require destination to exist
basic support for pickling FS instances
whoops, remove debugging print
support for the "with" statement in S3FS
OSFS: don't let removedirs() recurse beyond the FS root
make S3FS pickleable
Uniform "overwrite" behaviour for copy/move/copydir/movedir.
New "force" argument to removedir().
Work in progress with an FS->Fuse adapter. Added a default implementation of xattr to base.py, fixed some issues in memoryfs
Added some instructions under the comments
S3FS: use get_bucket rather than create_bucket until we know the bucket doesn't exist.
More work on xattr support
utility method for S3FS: get_total_size
making a branch to play around with some of the APIs
Condense and cleanup helpers.py/utils.py
first cut at a new Exception heirarchy