Added SingletonPerThread provider

[sirkonst]

Very useful for me :-)

[coveralls]

Coverage decreased (-1.9%) to 98.123% when pulling 042a795 on sirkonst:feature/singleton_per_thread into 1c47f73 on ets-labs:master.

[rmk135]

Hello,

Just wanted to say "Thanks". I will take a look a bit latter.

Roman

[rmk135]

Hello Konstantin,

I've reworked a bit your idea and merged it in terms of PR #132. Also I've added a special section in documentation about using singletons in multi-threading applications.

I productized new version with number 2.1.0 (http://python-dependency-injector.ets-labs.org/en/stable/main/changelog.html) and it's been available on PyPi (https://pypi.python.org/pypi/dependency_injector/2.1.0), so you're welcome to upgrade.

PS: Thanks a lot for your contribution, I have added you in a list of contributors (https://github.com/ets-labs/python-dependency-injector/blob/master/CONTRIBUTORS.rst). Hope you are fine with that ;)

Thanks,
Roman

[sirkonst]

Thanks! Great library!

[rmk135]

Thank you 😊