Configure sass-spec correctly

[kwonoj]

It isn's clear if test setup is correct

libsass-asm/circle.sh

Lines 19 to 25 in 798a4ab

	git checkout v3.5.4
	git cherry-pick 106e6d4c2e35bda22238539e978acdd60e153fb9
	# The following tests pass but were marked as TODO for libsass: (i.e https://travis-ci.org/sass/libsass/jobs/399963285)
	# TODO: why --probe-todo doesn't work?
	rm -rf spec/libsass-closed-issues/issue_2360
	rm -rf spec/sass/import/unquoted

, --probe-todo doesn't seem to work and manually check out specific version tag for sass-spec. Need to figure out correct setup for tests.