Update README.md

The command for git-cloning the repo is using a Git URL with read/write access, which doesn't work for people without write access to the repo.
Merge pull request #65 from skddc/patch-1

Fix repo URL in README
Added UTXO to README. #68
update bitcore lib to 0.1.18
Update TransactionDb.js
add missing updates
Merge remote-tracking branch 'origin/update-bitcore' into update-bitcore
Merge pull request #71 from bitalo/update-bitcore

update bitcore = 0.1.18
Merge pull request #70 from cmgustavo/bug/01readme

Added UTXO to README. #68
adoptions for dogecoin testnet