Ignore non-directories when scanning for plugins.
Ignore non-directories when scanning for plugins.

This keeps OS X's .DS_Store from getting picked up as a plugin when using `disabled_plugins` and not `enabled_plugins`.

nrc/dxr,jay-z007/dxr,jay-z007/dxr,pombredanne/dxr,nrc/dxr,KiemVM/Mozilla--dxr,jay-z007/dxr,pelmers/dxr,jbradberry/dxr,pelmers/dxr,KiemVM/Mozilla--dxr,pombredanne/dxr,pelmers/dxr,srenatus/dxr,kleintom/dxr,jay-z007/dxr,erikrose/dxr,jay-z007/dxr,gartung/dxr,gartung/dxr,jbradberry/dxr,pelmers/dxr,kleintom/dxr,KiemVM/Mozilla--dxr,nrc/dxr,KiemVM/Mozilla--dxr,bozzmob/dxr,KiemVM/Mozilla--dxr,pelmers/dxr,erikrose/dxr,jbradberry/dxr,bozzmob/dxr,jay-z007/dxr,gartung/dxr,jay-z007/dxr,bozzmob/dxr,pombredanne/dxr,srenatus/dxr,gartung/dxr,jbradberry/dxr,kleintom/dxr,gartung/dxr,pombredanne/dxr,srenatus/dxr,erikrose/dxr,srenatus/dxr,gartung/dxr,pombredanne/dxr,kleintom/dxr,srenatus/dxr,bozzmob/dxr,kleintom/dxr,srenatus/dxr,bozzmob/dxr,bozzmob/dxr,pombredanne/dxr,kleintom/dxr,jbradberry/dxr,bozzmob/dxr,pombredanne/dxr,nrc/dxr,jbradberry/dxr,erikrose/dxr,KiemVM/Mozilla--dxr,pelmers/dxr,erikrose/dxr,kleintom/dxr,jbradberry/dxr,nrc/dxr,gartung/dxr,pelmers/dxr,nrc/dxr