Merge branch 'popover' into dev

Merging changes from popover branch of development.
Started using php
Ignore temporary vim files
Redirect all requests to index.php
Removed old math page
Load in content subfiles when requested.
Moved content files into subdirectory
Added links to subpages in the tab descriptions
Corrected to read: natural science
Removed old cs file
Merge branch 'templating' into dev

Merging templating feature into dev branch.
Merge branch 'dev' into popover

Merging dev into popover branch.