Add the default monospace font stack for <code> elements

Unfortunately <code> elements weren't getting the monospace font stack they
deserved so they looked a little out of place. :lipstick:
add head_ref_restored
Squashing and merging an update
Merge pull request #472 from github/update-1396638735

Opening a Pull Request for alternate updates
Sync changes from upstream repository
Merge pull request #473 from github/update-1396645501

Sync changes from upstream repository
updating a bunch of links to the developer site to be https
fix the documentation for github signature
Merge pull request #475 from konklone/fix_signature

Fix docs for name of GitHub signature request header
reverting incidental version qualifier
document search api incomplete_results attribute
Updating to use GitHub default font stack

- Make the <code> font stack more consistent from GitHub.com.
- Refactor code/pre selector rules to be generic enough to catch all
the lingering code blocks.
Merge pull request #474 from konklone/https

Updates links to developer.github.com to be HTTPS
Sync changes from upstream repository
Merge pull request #476 from github/update-1396973742

Sync changes from upstream repository
Sync changes from upstream repository
Merge pull request #477 from github/update-1396984071

Sync changes from upstream repository
Merge pull request #427 from jacobbednarz/update-code-blocks-to-use-correct-monospace-font

Add the default monospace font stack for <code> elements
Sync changes from upstream repository
Merge pull request #478 from github/update-1397061603

Sync changes from upstream repository