README.md: write a workaround to build goji

goji does not currently build with the latest version
of pprint.

this commit describes a workaround to build it with
a compatible version of pprint.

Signed-off-by: Ion Alberdi <nolaridebi@gmail.com>
workaround: include sources of the old PPrint
Merge branch 'master' of https://github.com/klakplok/goji