[refactor] Require webhook scripts list to be passed as object to constructor; Load webhook scripts in parallel

Also supports mixed type of shell and node scripts.
Also supports differing urlPath and localPath.

New webhook scripts object:
"urlPath":
  "type": ["node"|"shell"] (optional)
  "dir": "localPath (relative to baseDir)" (optional)
  "mod": [loaded CommonJS module with hook fn] (optional)

For default type and urlPath == localPath, use: "urlPath": true
[deps] Express 4 syntax
[log] better logging and errors
[build] Cakefile for iced-runtime, --bare

--bare because closure wrapper is unnecessary for node scripts.
[doc] New syntax for hook scripts/modules
[release] Version 0.1.0