Fix: Handle param _readableState added by NodeJS

Should help (fix?) with issue #2
package.json now fixes modules’ version

(cherry picked from commit d77880a6ce78513e9f54c02a96182448b31e5d6f)
Add missing infos in CHANGELOG
Merge branch 'next'

* next:
  Add missing infos in CHANGELOG
  Add default 'clean' task in main gulpfile.js
  Added convenience default clean task
  package.json now fixes modules’ version
  Fix: Handle param _readableState added by NodeJS
  Returns (and show) generation errors
  Fix createDir
  example: Remove ugly tests
  Clean code
  Add helper `require` to import JS files in templates
  Remove cleanEnv ⇒ no need to global anymore
  Simplify cleanEnv
  example: Add example ‘stylus’
  gulp: Add defineTasks()
  gulp: init() now returns the config object
  example: Move example into example/vanilla

Conflicts:
	package.json
Bump to 0.0.6
cli: Default src/dst dirs are now global paths

Relative paths were resolved against the gulpfile.js's directory.
readme: Fix example path
Display infos logs only in debug mode
Rename `url_to` into `pathTo`

This helper returns a path (`/xxx`), not an URL (`http://foo.com/xxx`).

The `url_to` helper still works but displays a warning.

The new syntax uses camelCase to allow the introduction of a real
`urlTo` helper (which returns an URL).
Add `pathToHere` helper
Throw real errors

Stop using `throw "error"`,
use `throw new Error("error")` instead
Add `urlTo` and `urlToHere` helpers

Note: they need the param `prismic-url-base` to be
specified.
Show stack trace of thrown errors
Use dot syntax instead of static string to access attribute
Make the noCache option more clear