Fix issue #829
Fixes #748 - adding comment in to robots.txt
Merge pull request #830 from jacquerie/master

Fix issue #829
Update for #824 - allows for two links to each of the principles
Merge branch 'master' of https://github.com/google/WebFundamentals
Fixed #820 - added periods to TL;DR in two performance docs, as well as to one ordered list.
Merge branch 'master' of https://github.com/google/WebFundamentals
Fix issue #833
Merge pull request #834 from jacquerie/master

Fix issue #833
Fixed #819 - added link to media queries doc in performance doc and added periods to TL;DR.
Merge branch 'master' of https://github.com/google/WebFundamentals
Fixed #819 again - tested link live and it wasn't working.
Fix #818 - add link to viewport in performance doc and added periods to TL;DR