`sed -r` is not present on some BSD based systems, including MacOSX
Darwin. perl is standard pretty much everywhere, so this a more
reliable way to test.
Since this is only used for tests, any performance differences
should not matter significantly.
`grep -P` gives access to the PCRE matching engine, which is nice,
however, the version of grep shipped on many BSD systems (including
Darwin) does not have this flag.
Currently, `grep -P` was being used in the `_includes()` test helper.
For cross platform compatibility in tests, do not rely upon this option.
Luckily, all existing tests seem to work fine without it already!
don’t bother on macosx (preinstalled) or if the test matrix for that
box isn’t going to be testing in zsh.
this should speed up test runs for most cases, and later we can define
fast_failure and not have to wait for the longer ones.
Requires beta access, thankfully the travis gods have blessed us for the
main repo and my fork!
This should allow us to make sure scm_breeze operates reliably in both
Linux and BSD/Darwin, because there are small shell differences
(especially with default tools) that are causing errors I noticed on
MacOSX.
