I'm using MAMP installed on Yosemite 10.10.2 installed at /Applications/MAMP. Everything worked perfectly when I had the files in the web root which is /Applications/MAMP/htdocs/. I then created a subdirectory named gtstore (/Applications/MAMP/htdocs/gtstore) and moved all the files into that directory. The code shown is copy & pasted from the files.
I then made the edits shown in the Chapter 7, Server Setup "Using a Subdirectory" sidebar. This is the suggested change I made to .htaccess. The rest of the file was unchanged.