Usage of requests.Session

[ZuluPro]

I just experienced the following error:

File "/usr/local/lib/python2.7/dist-packages/SoftLayer/API.py", line 360, in call
    return self.client.call(self.name, name, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/SoftLayer/API.py", line 263, in call
    return self.transport(request)
  File "/usr/local/lib/python2.7/dist-packages/SoftLayer/transports.py", line 199, in __call__
    raise exceptions.TransportError(0, str(ex))
SoftLayer.exceptions.TransportError: TransportError(0): ('Connection broken: error("(104, \'ECONNRESET\')",)', error("(104, 'ECONNRESET')",))

So I though about the change the transport implementation to allow retries in case connection error.

This also create memoized session.

[coveralls]

Coverage increased (+0.02%) to 86.362% when pulling 2e416b4 on ZuluPro:requests into 5f16b02 on softlayer:master.

[coveralls]

Coverage increased (+0.02%) to 86.362% when pulling 43ea8f6 on ZuluPro:requests into 5f16b02 on softlayer:master.

[allmightyspiff]

I'm a little hesitant to make a library wide retry right now. I do have a @Retry decorator that I've been adding where I feel it is safe.

I will review this though to see if using the requests retry function works well. Mostly I'm concerned that this might lead to placeOrder calls putting in multiple orders in certain cases.

Also, please make sure the travis-ci build finishes successfully as well.

[ZuluPro]

@allmightyspiff
Actually the retries are implemented only on ConnectionError.
That means it will not retry when fail to read response or with bad status code,
Only TCP Error, before HTTP ones.

[allmightyspiff]

I'll merge this in #916