change pretty to compact
Update jwt.go

Hi! I'm using Go 1.0.2 and encountered "src/github.com/dgrijalva/jwt-go/jwt.go:87: function ends without a return statement". This commit returns explicit at the end of the function.
Merge pull request #17 from cryptix/prettierPretty

change pretty to compact
Merge pull request #18 from aspic/patch-1

Update jwt.go