Add rate limiting exceptions

[skion]

This adds two exception types to enable users to detect rate limited calls which were previously swallowed and converted into a generic InvalidArgumentError, making it impossible to detect rate limiting situations and pass that information through to the end user.

This is being discussed in #666.

I chose to inherit from the ResourceExhaustedError base exception, which seemed to make most sense.

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[skion]

@pragatimodi Since you are assigned to #666, would you be able to check this out?

[skion]

@jonathanedey I see you are mostly maintaining this repo now, is this something you could have a look at?