Don't add rowspan/colspan if it's 1.
Just a small thing I noticed in a [footnote here](https://danluu.com/web-bloat/#appendix-irony). Probably can't do much about the extra classes, but rowspan/colspan seem like easy fixes to save a few bytes per row/col and it's already done in the other code path.

Don't really know if this is major enough to deserve a what's new entry.

 - [ ] ~~closes #xxxx~~ - N/A
 - [x] tests added / passed
 - [x] passes ``git diff upstream/master | flake8 --diff``
 - [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15403?src=pr&el=h1) Report
> Merging [#15403](https://codecov.io/gh/pandas-dev/pandas/pull/15403?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/9b5d8488e8184da0507c09482f23ebfff34ecc43?src=pr&el=desc) will **decrease** coverage by `-0.01%`.
> The diff coverage is `100%`.


```diff
@@            Coverage Diff             @@
##           master   #15403      +/-   ##
==========================================
- Coverage   90.37%   90.37%   -0.01%     
==========================================
  Files         135      135              
  Lines       49454    49463       +9     
==========================================
+ Hits        44694    44702       +8     
- Misses       4760     4761       +1
```


| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/15403?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/formats/style.py](https://codecov.io/gh/pandas-dev/pandas/compare/9b5d8488e8184da0507c09482f23ebfff34ecc43...9a8fcee1b2fba721543478cd9dbbb3076c0efd03?src=pr&el=tree#diff-cGFuZGFzL2Zvcm1hdHMvc3R5bGUucHk=) | `96.17% <100%> (+0.11%)` | :white_check_mark: |
| [pandas/core/common.py](https://codecov.io/gh/pandas-dev/pandas/compare/9b5d8488e8184da0507c09482f23ebfff34ecc43...9a8fcee1b2fba721543478cd9dbbb3076c0efd03?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tbW9uLnB5) | `91.02% <ø> (-0.34%)` | :x: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/15403?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/15403?src=pr&el=footer). Last update [9b5d848...9a8fcee](https://codecov.io/gh/pandas-dev/pandas/compare/9b5d8488e8184da0507c09482f23ebfff34ecc43...9a8fcee1b2fba721543478cd9dbbb3076c0efd03?el=footer&src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments). @QuLogic thanks. Could you check and see if we have any tests of colspan > 1 when there's a MultiIndex in the columns? I see we have one for rowspan > 1 with a MI in the index, but didn't see one for the columns. I'm not sure where it is, but codecov says it's hitting both `colspan > 1` and `rowspan > 1`. is there any visible effect of this? You can add a whatsnew entry with this PR number just to document. Maybe under Other Enhancements. lgtm. otherwise.  It should be invisible to the user (other than the tables being costing
fewer KB)

On Thu, Feb 16, 2017 at 8:30 AM, Jeff Reback <notifications@github.com>
wrote:

> is there any visible effect of this? You can add a whatsnew entry with
> this PR number just to document. Maybe under Other Enhancements. lgtm.
> otherwise.
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <https://github.com/pandas-dev/pandas/pull/15403#issuecomment-280345083>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/ABQHIjzxvYx50ntO5WWkkLn3TKQnmUgfks5rdF2MgaJpZM4MBE3l>
> .
>
 thanks @QuLogic 