Revert "Updates nupic.core to c5e8e3a7d03b6edaa20276cda5fa1c13c7836711."

This reverts commit ae7ac7f089f6379496dc43b3c52d9ccefdb9a8c0.

@rhyolight - you merged this recently but it results in mismatch in nupic/nupic.core. I have an outstanding PR to fix that (#1189) but I can't debug it due to build problems. My proposal is that we revent the SHA upgrade now and I will work with @oxtopus to get the build situation resolved and subsequently get #1189 merged.