ENH: function to split dict over an iterable

One thing I found I have had to do that might be useful to include is to split a dictionary on an iterable value. The user would provide a dictionary and a key. The function would then return an iterator of dictionaries, each dictionary having one value from the key. It could be called splitvalue, perhaps.

So to give an example:

>>> a = {'key1': 1, 'key2': a, 'key3': [0, 1, 2, 3]}
>>> list(dictoolz.splitvalue(a, 'key3'))
[{'key1': 1, 'key2': 'a', 'key3': 0},
{'key1': 1, 'key2': 'a', 'key3': 1},
{'key1': 1, 'key2': 'a', 'key3': 2},
{'key1': 1, 'key2': 'a', 'key3': 3}]

The issue names no files, tests, or entry points; first inspect the existing dictionary utilities and their tests to find the public API and conventions. Use the supplied splitvalue example as the target behavior, clarify edge cases such as missing or non-iterable keys, and verify the relevant tests and full suite.