Revert "removed reference to avx option from README.md"

This reverts commit 0add47b3519112090807033af5c053df604b4d61.
this yum install has other dependencies

Revert "Revert "removed reference to avx option from README.md""

This reverts commit 384d65c35526b8febd7207c70184274c63c567e3.