Merge pull request #1 from ripple/master

catching up to master
fixed usage syntax for --json flag
removed outdated/incomplete docs and added link to dev portal
Merge branch 'master' of github.com:ripple/gatewayd
Merge pull request #259 from mDuo13/new_readme

New simpler readme, removed outdated docs [2]
Merge pull request #266 from ripple/develop

[DOC] Move api, install documentation to dev.ripple.com