Assume tests/ when no SOURCE_PATH is specified

If tests/ does not exist, print the old output from CLILib.
The HackTest output would be confusing, namely:
Uncaught exception 'Facebook\HackTest\InvalidTestFileException'
with message 'File or directory (tests) not found'
It would be unclear where the name tests came from.

Update fbexpect to 2.8.1 (#108)

permit HSL IO v0.3

Replace 'writeAsync' with 'writeAllAsync' in more places

Prevents truncated output, and fixes support for future
hsl-experimental release

replace file_exists() call with could_include()

Support HHVM 4.64

Temporarily disable hhast in CI as it has not yet been updated for new
hh-cliilb

Support (and require) HSL IO 0.2

array -> varray in shape

Update dependencies

- explicitly depend on HSL-IO v0.1 API
- permit type-assert v4

[easy] make VerboseCLIOutput forward compatible with future HSL IO ch…

…ange

HSL IO is changing `writeAsync()` to return `Awaitable<int>`, but the
function here is `Awaitable<void>` - `return await` is no longer
compatible.

Tangentially, I'm a little surprised that explicit return values are OK
in `Awaitable` functions :/