Ignore .DS_Store files
Ignore .DS_Store files

Everybody keeps adding this ignore rule to their github branches, so
let's just go ahead and add it to master .gitignore file.  The .DS_Store
file is created by MacOS X.

mico/Mephisto-fork,mephistorb/mephisto,rwdaigle/old.ryandaigle.com,technoweenie/mephisto,mephistorb/mephisto,mat/mephisto,jgoggles/mephisto,rwdaigle/old.ryandaigle.com,emk/mephisto,mico/Mephisto-fork,emk/mephisto,mat/mephisto,technoweenie/mephisto,jgoggles/mephisto