REPR: kwds in DateOffset

[cancan101]

Currently the signature for constructing most DateOffset is (n, **kwds).

Optional ags are then read using get(key) from the kwds and required args using [key]. This is fine, but it leaves what was extracted from kwds still in kwds leading to a redundant str or repr:

Week(weekday=0)
<1 Week: kwds={'weekday': 0}, weekday=0>

I would recommend using pop instead of get and using del after reading required values.

Thoughts?

[jreback]

you can just try it and see if it breaks tests (use a separate branch); if it looks ok, then submit a PR

(maybe add a test for the new repr)

[cancan101]

Taking a look at how kwds is used (e.g for copy) by the base class, DateOffset, it will be easier to cleanup how repr works rather than changing what is left in kwds.

[jreback]

there's prob not a lot of testing on this area of pandas....go for it!