[DOC] Add installation guide for Mac
[FEATURE] Reorganize ProcessManager, create ProcessSet.

[TASK] Rename GatewayProcessManager to ProcessManager.

[TASK] Rename GatewaydProcessSet to ProcessSet.
Merge pull request #260 from ripple/install-on-mac

[DOC] Add installation guide for Mac
[TASK] Clean up ProcessManager behavior.
Merge pull request #265 from ripple/processes

[FEATURE] Reorganize ProcessManager, create ProcessSet.
[DOC] Correct documentation, config.json not config.js.
Merge pull request #274 from ripple/fix-install-doc

[DOC] Correct documentation, config.json not config.js.
[DOC] Correct documentation, config.json not config.js.

[FOLD] Use config.json not config.js in mac install doc.
[TASK] Add release notes, bump minor version.
Merge pull request #275 from ripple/release-3.26.0-rc1

Release 3.26.0 rc1