Add a failing tests for options in pub keys.

Current code explicitly expects exactly 2 fields, which is not correct.

Added tests which have options (at the start) and/or comment (at the
end) to check that we work in all possible cases.
Fix the bug in keys with comments.

Do this by iterating through the fields until finding the key type, and
then using the next field. This is the most bullet proof method that I can think of,
but this code is also fragile about future new key formats now :(
Merge pull request #136 from bobtfish/fix_options_in_public_keys

Fix options in public keys