Adding initial commit for the blocking functionality in the get func…

[JoJo10Smith]

This will add the blocking functionality to the get function with the following optional parameters:

• max_attempts: this will determine how many attempts to try and find a free object in the specified time
• max_timeout: the maximum time in seconds to try and connect after which the normal functionality of the method will occur.

This is in response to issue #519

[JoJo10Smith]

I realized that there was a better implementation which I will explain below:

• Get the current_time and set an end_time to be the current_time + optional timeout, if timeout is not given then set the end_time = current_time.
• Start the function as usual but now while the current_time <= end_time keep trying to remove any free objects that have idled for too long.
• If a free object is then return obj, if not then get the current_time again, if it is before the end_time try removing free objects again.
• Once the time limit is reached if there are no free objects (because the while loop has not been broken) we create one, if there are too many raise a RuntimeError. else return obj

I look forward to hearing any feedback/ responding to questions
Thanks
Jordan

In response to #519

[jogo]

thanks for the PR, a few inline comments and once those are sorted out better inline documentation, unit tests and updating the changelog would be great.

[jogo]

Why not use keyword arguments with defaults here? That and a docstring will make this feature easier to find and documented in our code docs.

[jogo]

if I understand this correctly this results in busy waiting all while holding a lock. Which seems like a behavior we don't want to introduce.