[BOUNTY COMPLETD] fix DEMA example strategy

[briancrypto]

For us newbies.. how do we add the fixes to Gekko?

I figured it out.. 
For all other newbies like me.. lol. here you go..

I followed the comment "A PR is currently proposed that fixes the DEMA: https://github.com/askmike/gekko/pull/1822"

I viewed the files changed.. https://github.com/askmike/gekko/pull/1822/files

Then I found those updated files by going back to the code.. https://github.com/askmike/gekko

I downloaded the updated files and replaced the old ones.