Simple sending ether to contract address works the same as calling buyWithLimit() with zero limit.
But what is really needed and NOT explained in your article - how to claim tokens and how to generate and register EOS key (without which yoo'll be unable to use tokens after EOS blockchain launch).
Also, if you contribute to a closed window this instruction in buyWithLimit()
assert(day >= today());
will throw exception. Transaction'll fail using all gas.
RE: How to contribute to a future period/window in the EOSCrowdsale using MyEtherWallet (MEW)