Merge pull request #40 from lukaslueg/master

Find tor-binary from PATH or via globbering for it
fix leftover conflict markers from pull-request
Use rST for README instead, to avoid pandoc build rule
fix rST markup for embedded URIs
More OS success reports (issue #42)
update Stem URI
add known users
Fix spelling of graphviz (issue-43)
move releases to their own file and page
couple improvements to first example
instructions for using virtualenv
documentation for build_local_tor_connection
Ability to create a circuit without specifying a path.
mention new feature
pass a keyword argument to circuit_closed, circuit_failed, stream_detach, stream_closed and stream_failed
fix up comments
remove unused code
output circuit path when loggin streams (in example)
issue #18: provide all flags with events

For several circuit and stream events, Tor may provide several flags (acutally
an unbounded number of flags) and previously only "REASON" was provided (as a
reason kwarg). Now, all flags are provided with both upper-case (as from Tor)
and lower-case versions, to facilitate method-signatures with the flags one
is interested in.
issue #44: provide password callback

instead of simply passing a password string around, TorControlProtocol
now accepts a password callable that may return a string or a Deferred
which callbacks with a string that is the password. This would allow
one to query the user for this if needed.