Test the examples on README in CI

[zaikunzhang]

Hi @jschueller ,

Due to https://github.com/libprima/prima/issues/108 and https://github.com/libprima/prima/issues/107 , I guess we need to test the examples on README in CI, literally and exactly.

"Stupid" tests are never stupid :P After working on PRIMA for more than three years, I have learned not to trust myself regarding code. I do not know what will happen before I have taken some "stupid" tests.

Thanks.

Zaikun