Provide default implementation for `data_repated`
Split from PeriodArray.

The previous implementation was not great, since failing to override it would result in `Series([NotImplementedError, NotImplementedError...])`. We could raise instead, forcing downstream arrays to implement it, or just repeat `data`. I opted for the latter, which integer_array was already doing. 
Hello @TomAugspurger! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`pandas/tests/extension/conftest.py`](https://github.com/TomAugspurger/pandas/blob/6834c52ec5edbe4ea29092e70dbee912ad10cf39/pandas/tests/extension/conftest.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/decimal/test_decimal.py`](https://github.com/TomAugspurger/pandas/blob/6834c52ec5edbe4ea29092e70dbee912ad10cf39/pandas/tests/extension/decimal/test_decimal.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/test_categorical.py`](https://github.com/TomAugspurger/pandas/blob/6834c52ec5edbe4ea29092e70dbee912ad10cf39/pandas/tests/extension/test_categorical.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/test_integer.py`](https://github.com/TomAugspurger/pandas/blob/6834c52ec5edbe4ea29092e70dbee912ad10cf39/pandas/tests/extension/test_integer.py) !

 - There are no PEP8 issues in the file [`pandas/tests/extension/test_interval.py`](https://github.com/TomAugspurger/pandas/blob/6834c52ec5edbe4ea29092e70dbee912ad10cf39/pandas/tests/extension/test_interval.py) !

 Travis failures is the unrelated s3 failure tracked in https://github.com/pandas-dev/pandas/issues/22934