Fixes to scope

as discssued in
https://github.com/twbs/bootstrap/issues/15117#issuecomment-63029993

- added ``scope="row"`` to row headers
- made sure row headers are actual ``<th>`` elements
- removed ``scope="col"`` where it was redundant
- simplified table examples with (to me) unnecessary
``rowspan``/``colspan`` (unless you really want complex tables, in which
case we would need full-on ``id`` and ``headers`` attributes to make
sure each table cell has an explicit association with the related header
cells - overkill, in my opinion)
- one table (in typography) left header-less, as it's more or less presentational (though its structure is still important, hence not adding ``role="presentation"``)
Add a target to generate the gh-pages files.

It sets `github: true` for us.
Update links (.../blob/master prefix) in markdown.
Center .icon-prev and .icon-next

Center .icon-prev and .icon-next the same way .glyphicon icon are.
And this is the html markup:
<a class="left carousel-control" href="#carousel-main-menu" role="button" data-slide="prev">
<span class="icon-prev" aria-hidden="true"></span>
</a>
Add CSS source maps reference to docs. Closes #15211

- update distribution file list with relevant files
- add a short reference to CSS source map purpose
- add link to Google Chrome developer network article
Fix copy/paste error
Merge pull request #15249 from dandv/patch-1

Fix copy/paste error
Merge pull request #15167 from vsn4ik/rem_blob_master_from_links

Remove redundant .../blob/master/ prefix in markdown.
Merge pull request #15238 from peterblazejewicz/docs/dist-update

Add CSS source maps reference to docs. Closes #15211
fix the run-on
fixes #15164: wrap disable pagination spans in another span
Fixes #15148: make the dropdown and dropup menus have the same margins
Fixes #15124: Restore .media-object
grunt
Fixes #15074: Fix the nesting problem with form control size variants
grunt
Alternate fix for #15250 with a more descriptive theme jumbotron
Fixes #15140: Restore more missing .media styles from shipping #14801
grunt
Fixes #15241: Add simple example to docs for collapse plugin