Add a location block for Nginx backend Twig edits

Signed-off-by: Gawain Lynch <gawain.lynch@gmail.com>
Merge pull request #88 from GawainLynch/nginx-fix

Add a location block for Nginx backend Twig edits
Updating installation.md, see https://github.com/bolt/bolt-docs/pull/88
Reverting Bob's nonsense duplication
started work on rewrite of extensions section
updates to testing procedure for extensions
Update extension example for tasks
Merge pull request #90 from GawainLynch/cron-dispatcher-example-code

Update extension example for tasks