Make equals without messages more resilient

When called without a message parameter the tests would fail under some
environments. I'm not clear on what is causing the failure, perhaps
ruby version, but this patch cleans up the issues there.
Expand literal syntax tests
Remove unused vars
Add LICENSE to built file

Fixes #411
Rebuild dist
Only allow 'this' or '..' to lead a path

Paths like 'outer/../key' raise an exception when compiling.
Merge pull request #414 from leshill/leading_context_only

Only allow `this` or `..` to lead a path