Decrease max-age Cache-control value used in examples to follow RFC

[sbocinec]

Default max-age Cache-control value in the project's README.md and tests suggest users to use very high value 630720000 (20y). RFC 2616 mentions the Expires value SHOULD NOT be more than 1y.

I suggest to use value of 31536000 (1y) in the doc/tests/examples to encourage this awesome project's users to be good netizens.