ENH: Pandas Series provide to_excel method
 - [x] closes #8825
 - [x] tests added / passed
 - [ ] passes ``git diff upstream/master | flake8 --diff``
 - [x] whatsnew entry

this prob needs to be added to ``api.rst`` as well Could you retrigger [this job](https://travis-ci.org/pandas-dev/pandas/jobs/180428431) ? Thanks @scls19fr The job fails because of a lint error. pls fix. ## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14780?src=pr) is 85.27% (diff: 100%)
> Merging [#14780](https://codecov.io/gh/pandas-dev/pandas/pull/14780?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

```diff
@@             master     #14780   diff @@
==========================================
  Files           144        144          
  Lines         50946      50953     +7   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43445      43452     +7   
  Misses         7501       7501          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [c0e13d1...0ab4876](https://codecov.io/gh/pandas-dev/pandas/compare/c0e13d1bccd4a783486eba8cc769db48a7875de8...0ab4876374078d8eafecb622c24d9e7a4fbe639e?src=pr) Thanks @sinhrks I didn't noticed because that's only for 1 job. pls rebase and push again @scls19fr Thanks a lot!