Ignore path suggestions if user does not have access permissions.

When compiling lists of completions, an uncaught exception may be thrown
if the current user does not have permissions to access a particular
directory.  Such paths frequently occur when typing "/" on a Windows
system.

Signed-off-by: Timothy McCoy <mccoy.m.tim@gmail.com>
Merge pull request #15 from timikoy/master

Fix #13 - Ignore path suggestions if user does not have access permissions.