[core] Add a CONTRIBUTING.md file to fix #245. Also addressed @jasontedor review, thanks!
[core] Add a CONTRIBUTING.md file to fix #245.
Also addressed @jasontedor review, thanks!

leschekhomann/YCSB,brianfrankcooper/YCSB,brianfrankcooper/YCSB,brianfrankcooper/YCSB,brianfrankcooper/YCSB,cricket007/YCSB,leschekhomann/YCSB,cricket007/YCSB,ChristianNavolskyi/YCSB,ChristianNavolskyi/YCSB,ChristianNavolskyi/YCSB,cricket007/YCSB,cricket007/YCSB,leschekhomann/YCSB,leschekhomann/YCSB,ChristianNavolskyi/YCSB