Update README.md

Updated link for build instructions.
Merge pull request #186 from shobute/patch-1

Update README.md
Re-enable "getheaders" network command.
Merge pull request #188 from domob1812/enable-getheader

Re-enable "getheaders" network command.
Enforce a minimum name coin amount.

Introduce a softfork that enforces a minimum amount of locked coins for
each (newly updated) name.
Reject tx with too low fee from mempool also before fork.

For inclusion into mempool and newly mined blocks, reject name
transactions with too little locked coins even before the fork point.