Remove old NPM based third-party installs.

[abose]

As we are using deprecated node version 6.17, we need to remove old npm-based deps to enable node to upgrade. The deps in the third-party folder are tested and functional, so we will be keeping a copy in the source.

Reinstating functionality is done in #10

• Code mirror Codemirror direct integration #41
• less Directly integrating less  #42
• preact-compat Direct integration preact-compat, simulate-event, xtend, acorn #43
• simulate-event Direct integration preact-compat, simulate-event, xtend, acorn #43
• extend Direct integration preact-compat, simulate-event, xtend, acorn #43
• acorn Direct integration preact-compat, simulate-event, xtend, acorn #43
• preact webpack removal. #44
• preact-test-utils webpack removal. #44
• semver.browser.js webpack removal. #44

[abose]

Phoenix can now load in a browser without npm install required on the repo.
Closing.

Updates of third party libs is covered under #10