Fix error propagation from @ failures.

Really fixes alecthomas#185.

Generated .String() functions now return the correct value.

Fixes alecthomas#201.

Added newline to example in README

Fix envars with numbers.

Fixes alecthomas#138.

Fix bug where --help doesn't terminate.

--help exits with 0 (fixes alecthomas#136), added UsageWriter() and E…

…rrorWriter() (fixes alecthomas#137)

These writer functions should be preferred over .Writer().

Fix usage code block indentation issue.

Prevent examples from pulling in dependencies.

Fixes alecthomas#105.

Add HexBytes.

Simplify guesswidth.