implement MarshalBinary and UnmarshalBinary; no tests yet
Adding simple test for binary marshaling and unmarshaling.
Adding third party caviat to the test for binary marshaling and unmarshaling.
Adding doc string to binaray marshaling/unmarshaling test.
Re-adding line removed by mistake.
Copying is not necessary.
Removing useless import.
Fixing docstring.
Fixing a bug related to caveat location.
Adding test to check binary marshaling against libmacaroon.
Removed useless comment.
Checking error.
Declare variables instead of instantiate.
Merge pull request #14 from vds/013-marshalbinary

Fix bugs in binary marshal/unmarshal code and add tests.
Merge branch '013-marshalbinary' of github.com:rogpeppe/macaroon
Merge remote-tracking branch 'rogpeppe/master'

Conflicts:
	marshal.go