Handbook/intro Core language link is dead

[simonhughes22]

The "core language" link http://docs.witheve.com/handbook/core-language on the bottom of http://docs.witheve.com/handbook/intro/ is a dead link.

[cmontella]

Fixed: witheve/docs#37

The core language page is just blank right now though.... it's more of a header for the section, but it should have some meat to it. Going to track fixing that here: witheve/docs#38