Pass different parameters to mktemp on OSX

[mlopes]

[mlopes]

Fixes #3

[nwinkler]

Any updates on getting this merged, @ztombol?

[peshay]

@mlopes since it seems this repo is not longer maintained, I started my own fork and working on some changes there: https://github.com/peshay/bats-file/tree/patch-1 I'll also integrate your suggestion from here to use mktemp -d -- "${BATS_TMPDIR}${template}" 2>&1 but I make no difference for Darwin OS or not, because it works for all systems. Actually still 3 tests fail for me on macOS and I need to further investigate