add test for lsat fixture and change challenge parsing

[bucko13]

Partly resolves #4. The other part seems related to the macaroon library being used. It either has a bug or has deliberately forked from the macaroon standard and will need to be replaced. I'm hoping for the former.

In the meantime, this fix still addresses the first error reported.

The issue was reported here

[bucko13]

This adds a test for the macaroon from another library and since that's not working right now, that one test will fail.

[jacohend]

I see these travis failures:

tests/lsat.spec.ts(9,1): error TS6133: 'importMacaroon' is declared but its value is never read.
tests/lsat.spec.ts(9,32): error TS2307: Cannot find module 'macaroon' or its corresponding type declarations.

[bucko13]

Ah thanks, forgot some cleanup. Unfortunately the tests will still fail since I added a test for the golang macaroon and that's not supported yet in the current macaroon lib. Debating whether or not to just put this fix in with the broken build and then either separately wait to upgrade the macaroon dep or go through the laborious process of ripping out the existing macaroon library...

[bucko13]

closing in favor of #8