Rename init command to create
-debug option changed to -verbose
API url changed from 'xy/raw' to 'raw/xy'
Added mercurial to the list of build requirements

If mercurial isn't installed, the buildem code will fail while trying to
install Go.
Web client link changed to dvid-console

The old link was pointing to a repository that no longer exists.
Merge pull request #50 from neomorphic/master

README modifications