BUG: astype(str) on datetimelike index #10442
closes #10442 

fix for the bug: Convert datetimelike index to strings with astype(str)
going to send pull request for test 

I added all the tests..please let me know if I need to add anything else.
 sounds fine now, let me know if I need to add anythingelse
 pls add a note in whatsnew for 0.17.1 (enhancements). squash as well.
 going to need tests for `Series.astype(str)` as well (put near tests in test_series or tseries/tests/test_timeseries.py wherever the existing tests for .astype are), add the issue as a comment in the tests.
 @jreback 
there is no v0.17.1.txt for 0.17.1 in whatsnew folder.
 rebase on master
i put it their 2 days ago
 @hamedhsn can you update
 @jreback sorry, what do I need to update?
 comments above, needs a rebase as well
 @jreback did that.
Thanks
 couple of comments. pls squash as well
 @jreback sorry that I am asking..how can I squash the last few commits to one. I tried a few different approaches without a luck.
 http://pandas.pydata.org/pandas-docs/stable/contributing.html#contributing-your-changes-to-pandas
 @jreback squashed all the commits into one.
 you need to make sure you force push too.

```
git checkout thisbranch
git rebase -i master
```

squash (put a s by each commit)

```
git push yourremote thisbranch -f
```
 @jreback did that. thanks
 @jreback should be fine now.
 ok @hamedhsn ping on green.
 @jreback strange, not sure why test is failed. both sides are object type but it raises this error..
AssertionError: [index] Expected object to be of type class 'pandas.core.index.Index', 
found class 'pandas.core.series.Series' instead 

I tried the test with both side same nothing to do with astype but still get the same error
result = pd.Series(pd.date_range('2012-01-01', periods=3))
expected = result
tm.assert_index_equal(result, expected)
 @jreback it is fine now.
 thanks!
