BUG: Convert data elements when dtype=str in Series constructor with …
…int/float list

- [ ] closes #16605
- [ ] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Not sure if my solution is correct but it seems to resolve the issue and pass the tests.
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=h1) Report
> :exclamation: No coverage uploaded for pull request base (`master@07d8c2d`). [Click here to learn what that means](https://docs.codecov.io/docs/error-reference#section-missing-base-commit).
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/18795/graphs/tree.svg?height=150&width=650&token=eZ4WkYLtcO&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=tree)

```diff
@@            Coverage Diff            @@
##             master   #18795   +/-   ##
=========================================
  Coverage          ?   91.62%           
=========================================
  Files             ?      154           
  Lines             ?    51410           
  Branches          ?        0           
=========================================
  Hits              ?    47106           
  Misses            ?     4304           
  Partials          ?        0
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `89.49% <100%> (?)` | |
| #single | `40.84% <100%> (?)` | |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/series.py](https://codecov.io/gh/pandas-dev/pandas/pull/18795/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvc2VyaWVzLnB5) | `94.83% <100%> (ø)` | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=footer). Last update [07d8c2d...11542e9](https://codecov.io/gh/pandas-dev/pandas/pull/18795?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Hello @reidy-p! Thanks for updating the PR.







Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on December 19, 2017 at 21:34 Hours UTC thanks @reidy-p 