Error if dataprovider keys include periods

[fredemmott]

Fatal error: Uncaught exception 'OutOfBoundsException' with message 'Out of bounds vec access: invalid index 2' in /Users/fredemmott/code/user-documentation/vendor/hhvm/hacktest/src/HackTestCLI.hack:62

[fredemmott]

Might not be needed, now that dataproviders are no longer encoded. Will leave open until there's a unit test.