add report bug link to frozen header
authenticate user for gallery pagination page
Merge pull request #496 from code-dot-org/frozen-header

add report bug link to frozen header
Merge branch 'staging' of github.com:code-dot-org/code-dot-org into staging
fix short codes for new hoc tutorials
Merge pull request #498 from code-dot-org/staging

DTT
Merge pull request #499 from code-dot-org/test

DTP