Added readme.md like in the issue#5

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KommuSoft wants to merge 2 commits intowmoss:masterfrom

KommuSoft:add-readme

Commits on Jul 13, 2019

make LargeWord serializable
KommuSoft
committed

Commits on Aug 25, 2019

added README as in issue #3 (https://github.com/wmoss/haskell-Crypto/issues/3)
KommuSoft
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