update octave hash for peaks_contourf
update octave hash for peaks_contourf

I know my octave behaves differently here and thus took the hash of Travis. Output looks fine.

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