add new contributor

I followed the steps in the README.md to try a local Stackage build, but it didn't work.  When running ./dist/build/Stackage/stackage check, I got

Checking Cabal version
Checking build plan
Found the following mismatches
OnlySimpleList "tar-0.4.0.1"
OnlySimpleList "utf8-string-0.3.8"
OnlySimpleList "zlib-0.5.4.2"
zsh: exit 1     ./dist/build/Stackage/stackage check

Thus I have not verified my packages to make sure they work in Stackage.