BUG: handle outofbounds datetimes in DatetimeConverter
xref #2579

This at least solves the direct negative consequence (erroring code by importing pandas) of registering our converters by default.

cc @ocehugo @tacaswell @TomAugspurger 
 ## [Current coverage](https://codecov.io/gh/pydata/pandas/pull/13801?src=pr) is 85.23% (diff: 100%)

> Merging [#13801](https://codecov.io/gh/pydata/pandas/pull/13801?src=pr) into [master](https://codecov.io/gh/pydata/pandas/branch/master?src=pr) will increase coverage by **<.01%**

``` diff
@@             master     #13801   diff @@
==========================================
  Files           140        140          
  Lines         50415      50415          
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          42970      42972     +2   
+ Misses         7445       7443     -2   
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [98c5b88...6b6b08e](https://codecov.io/gh/pydata/pandas/compare/98c5b88d6f9f7bb0afa4fbae49a045d93a1cb33f...6b6b08e4fe13f1de310cd25a184625aed114a178?src=pr)
 working fine ;). No conflict with matplotlib so far in my usage. thanks for that!
 @sinhrks @TomAugspurger OK to merge?
 @sinhrks further comments? If not, be my guest to merge :-)
 thx!
