Maintenance.

Various small things:

  * At some loss of functionality, avoid non-Go standard library
    dependency.

  * In the era of 'go build', deprecate Makefile

  * It seems 'encoding/xml' has learned some case sensitivity, so
    adjust the struct tag to take that into account, making tests pass
    again.

Signed-off-by: Daniel Farina <daniel@fdr.io>