Use smartdown version with markdown public API
Simplify smartdown presenters with markdown_to_html helper.
Merge pull request #1334 from alphagov/smartdown_html_to_markdown

[MERGE THIRD] Use smartdown version with markdown public API
Animal example for NOT predicates.
Animal example update for OR predicates.
Merge pull request #1328 from alphagov/not_and_or

Not and or
Fix parsing error in spl question.
Merge pull request #1337 from alphagov/fix_newline_bug

Fix parsing error in spl question.
Marriage Abroad SA - Content update
Merge pull request #1339 from alphagov/marriage_abroad_december_fc_update

Marriage Abroad SA - Content update
Make install.sh executable

- This script is designed to be executed, so permissions should be updated accoringly
Merge pull request #1341 from alphagov/bugfix/update-install-perms

Make install.sh executable
Change table heading to span all columns

As mentioned by @tombye in [our card](https://www.agileplannerapp.com/boards/105200/cards/8701) on smart answer headings, the previous table headings didn't relate to the contents of the table.

This commit fixes that by:

- Changing the table heading to span the entire row, as with https://www.gov.uk/bank-holidays
- The 'start again' link is now below the previous answers table
- This commit does *not* attempt to add in any additional ARIA signalling, etc
Tests no longer look for '.link-right.restart'

- Previously our tests were looking for a `<th>` with `'.link-right.restart'`. These classes have been removed and so now we can just inspect the done questions section of the markup for the presence of the link
- Fixes test errors
Modify the layout of the 'Previous Answers' section

- Addresses the previous concerns around `with_title` logic. Now if there's no title, there's no heading
- Moves the title of the section into an `<h3>`, and restyles the 'start again' link, keeping it closer to the original design, but meaning that there's no semantic issues with the table headings, as was previously signalled.
Merge pull request #1342 from alphagov/refactor/previous-answers-heading

Change table heading to span all columns
amends from fc
Merge pull request #1343 from lutgendorff/patch-32

amends from fc
fixed typo
amends from fc