Throw non-string exceptions in asn1.js
Throw non-string exceptions in asn1.js

Issue #29. Dunno how useful this'll be. I'm thinking asn1.Error could be
errors in asn1 encode/decode, but we'll use things like TypeError to
deal with internal errors. Arguably all those can just throw strings for
random internal errors. Those are internal errors that we probably don't
never need to show to the user. Mainly we just want that exception to
propogate to top-level.

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