Merge pull request #24 from vbmithr/master

Generate doc for the Git backend as well.
Port to ocaml-git 1.0.0
Merge branch 'master' of github.com:samoht/irminsule

Conflicts:
	setup.ml
Fix an "intersting" bug when creating close-enough commits

If the commit date where close enough (ie. the same second), the commits were identical.
To fix that, we expose the date/origin contents in the commit constructor and we now pass them explicitely.
Remove the useless `stop_server` function
Make the Git backend a bit more convenient to use.

- Properly initialise the HEAD reference
- Allow to expand the filesystem and build the cache file on every commit (will be a bit slow, though, but convenient to use and debug)
Add a basic example on how to use the Git backend in a library
Write the new reference before creating the filesystem
Add some comments in the Git store example
Add a more robust notification mechanism

- Now the notification mechanism works for all backends (local, in-memory, remote)
  and works cross backends as well (ie. if a client watches a remote irminsule server
  which stores its state as a local Git store, then the client is notified everytime
  someone modifies the HEAD of the repo using Git command directly on the filesystem)

- For now on, using active polling on unix -- later we could use inotify and fsevents:
  the hook as an interface very similar to what ocaml-inotify-lwt would give us.

- the watch API takes a path as argument: notifications are sent every time someone
   creates, removes or modifies a file in that directory
Merge branch 'master' into notifications

Conflicts:
	lib/backend/irminGit.ml
	lib/backend/irminGit.mli
Update oasis autogen files
typo
fix merge bug
Be more explicit about installing the directory polling notifier.
Do not shout and fail if no notifier is installed.
Merge pull request #27 from samoht/notifications

Add a more robust notification mechanism
microkernel -> unikernel
Update CHANGES
Export the signatures of stores in backends.