Fix breakage from Bats v1.0.0, bump to Bats v1.0.1

[mbland]

https://github.com/bats-core/bats-core/releases/tag/v1.0.0, while honoring the same interface as v0.4.0, introduced a few changes that required some cleanup of our Bats utilities:

• bin/bats is no longer a symlink to libexec/bats, and the latter can no longer be invoked directly; hence _GO_BATS_PATH is now set to bin/bats.

• TAP output for skipped tests changed in bats-core/bats-core#19.

• run_bats_test_suite_in_isolation depended upon _GO_ROOTDIR and _GO_BATS_PATH, which led to bats not being able to find its libexec scripts. The bats path is now computed using command -v bats, which makes the library itself more portable.

• Some assertion-test-helpers output didn't end with a newline. This prevented the while loop used to replace sed in bats-core/bats-core#88 from reading the final line of output from the test. While this was fixed in bats-core/bats-core#99, updating the code to always emit newlines was still the right thing to do.

There was a bug in Bats v1.0.0 in setting BATS_CWD that broke the "assertion-test-helpers: failing assertion must disable shell options" test case. Specifically, stack trace paths that should've looked like:

tests/assertion-test-helpers.bash

instead looked like:

go-script-bash/tests/assertion-test-helpers.bash

This was fixed by bats-core/bats-core#98.

[coveralls]

Coverage decreased (-0.03%) to 94.997% when pulling f65af8ce04d2188c990543aed13f8cdb0fc901b4 on bats-v1.0.1 into c583616117bc87fb4bca17c4192e981312c0e102 on master.