Explictly add `private` to `runtests` path
Explictly add `private` to `runtests` path

Apparently, `private` is not accessible from within the `runtests` script.
So, we work around that issue.

RPeschke/matlab2tikz,egeerardyn/matlab2tikz,PeterPablo/matlab2tikz,LJeub/matlab2tikz,matlab2tikz/matlab2tikz,nidrosianDeath/matlab2tikz,egeerardyn/matlab2tikz,miscco/matlab2tikz,matlab2tikz/matlab2tikz