initial psc-package support (#82)

initial psc-package support (#82)

* Extract deps path

* Initial psc-package support

* index.js: `pscPackage` and `src` incompatibility warning

* index.js: make use of user-provided options

* index.js: make use of user-provided options: now for pscIdeColors

* index.js: remember depsPaths call result

* index.js: implemented appending user src paths with psc-packages'

* README.md: sync changes of pscPackage behavior

Also reflect pscPackage support in "Default options" section