Prep for 5.1.1 release

Push version number to 5.0.5

bump release version (RuntimeTools#599)

bump to new omr-agentcore and release (RuntimeTools#595)

Update README.md

Enable preloading and remove node-hc (RuntimeTools#499)

* enable preloading

* Deprecate node-hc in README

* remove node-hc

* Also mention NODE_OPTIONS

* Consolidate 2 different sections on preloading

* Also update version number in this PR

* Update version to 4.0.0

* Update version to 4.0.0

* Also note NODE_OPTIONS is in 6.12.0

* also remove launcher.js

bump version for packaging fix (RuntimeTools#501)

* bump version for packaging fix

* include omr-agentcore level

Merge pull request RuntimeTools#491 from stalleyj/https

Fix https outbound probe for Node 8.9.0+

Fix minor bug

Revert "Expose new GC types introduced in v8 version 4.6"