Added an exclusion for libcmockery to .gitignore .
Added an exclusion for libcmockery to .gitignore .

Typically we don't want to commit libraries to version control, but we (currently) need libcmockery in the project. We could remove that dependency by using Puppet to ensure that every machine had CMockery "properly" installed somewhere, but for now this works.
UMM-CSci-Systems/Traversing-Directories-starter,UMM-CSci-Systems/Traversing-Directories-starter