Flow weighting in clusterMAF

[ThomasGesseyJones]

As outlined in more detail in issue #38 the flows in clusterMAF were incorrectly weighted in __call__ and not weighted in log_prob. These led to incorrect sampling distributions and erroneous $D_{\rm KL}$ values respectively. This PR fixes #38 by now weighting the flows in both of these contexts in proportion to the sample weights in the corresponding clusters.

Additional minor changes:

• Minor version bump
• Casting of some inputs to tf.float32 when required to avoid type comparison errors
• Set n_init to 10 explicitly to stop deprecation warning from scikit
• Copying of some inputs to avoid unintended side effects
• Check no samples are outside prior ranges if set, discard and warn if any are
• Typo fixes in comments

[htjb]

Looks great! Thanks @ThomasGesseyJones! If the tests pass, please squash and merge.