util: fix bug in to_uid function

It must check for string_types, not str only.
Make sure rollover check compares against numbers, not strings.
tests: import unicode_literals from future
Merge branch 'lambdafu/rollover' of github.com:lambdafu/circus
#399 - Add a test for the FileStream class
added the example for bug #403
Merge pull request #399 from lambdafu/lambdafu/rollover

Make sure rollover check compares against numbers, not strings.
Merge pull request #397 from fsouza/master

util: fix bug in to_uid function
fixed the example. fixes #401
future must be on the top
fix the error type
example for #390
added some coverage for the stats full plugin
testing a memory leak with the ResourceWatcher plugin - relates #390
split the test into logical units
flake8-ed
changed the example - related to #403
Refs #404 - Rename watcher in service and add a deprecation warning in case of people using service
Merge pull request #405 from Natim/rollover

Refs #399 - Rollover add a test
Merge pull request #406 from Natim/issue-404

Refs #404 - Rename watcher in service