BUG: error calculating BusinessHourMixin.apply for long business hour per day
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew: handle the case where adding of business hour to the timestamp results in an ending time landing in the next business time period. Example

Input:
```python
bh = BusinessHour(n=4, start='00:00', end='23:00')
dt = datetime(2014, 7, 3, 22)
dt + bh
```
Expected:
```python
datetime(2014, 7, 4, 3)
```