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>
Merge pull request #2 from yetanotherion/master

README.md: write a workaround to build goji