Capture exceptions from `requests.posts`

[UmanShahzad]

It was discovered in https://github.com/ipinfo/python/issues/40 that a call to requests.posts in the sync handler was throwing an exception even when raise_on_fail=False.

This behavior can cause the loss of data from successful chunks in a >1000 size batch request if any of the chunks fail because of an error in requests.post.

TODO:

• [ ] Ensure the error is captured and not thrown if raise_on_fail=False.
• [ ] Check the async handler for similar issues.