Re-added Category Theory for Computing Science with udpated link.
Merge pull request #920 from jeffdc/master

Re-added Category Theory for Computing Science with updated link.
PDF about language php
Add EmberFlare and Dockyard tutorial
Merge pull request #922 from h0lyalg0rithm/patch-1

Add EmberFlare and Dockyard tutorial
Merge pull request #921 from gutierri/master

PDF about language php