Fixed Description of Writing an Interpreter in Go

[DomParfitt]

Updated the description for 'Writing an Interpreter in Go' to correct that it is the predecessor of 'Writing a Compiler in Go', not the successor.

Fixes issue #64.

Please fill in this template:

• Use a meaningful title for the pull request. Include the name of the resource added.
• Add a short sentence on why do you think the resource you're adding is awesome!
• Make sure your addition maintains the alphabtical order of the list.
• Make sure your addition contains a description besides the link.