Fasteners

- Fix 'ensure_tree' check on freebsd

- Use a tiny retry util helper class for performing process locking retries.

- Directly use monotonic.monotonic.
- Use BLATHER level for previously INFO/DEBUG statements.

- Add LICENSE in generated source tarballs
- Add a version.py file that can be used to extract the current version.

- Allow providing a non-standard (eventlet or other condition class) to the
r/w lock for cases where it is useful to do so.
- Instead of having the r/w lock take a find eventlet keyword argument, allow
for it to be provided a function that will be later called to get the
current thread. This allows for the current *hack* to be easily removed
by users (if they so desire).

- Add fastener logo (from openclipart).
- Ensure r/w writer -> reader -> writer lock acquisition.
- Attempt to use the monotonic pypi module if its installed for monotonically
increasing time on python versions where this is not built-in.