Pyhocon

* Add test for include substitution (gpoulin) [217]
* Fix self references when environment variables exist (anujkumar93) [219]
* Remove inactive Gitter channel from README (scottj97) [255]
* Fix STR_SUBSTITUTION, because ConfigSubstitution has no function raw_str (manso92) [227]
* Add support for package include (mrijken) [228]
* Fix required(file()) syntax (jrouly) [229]

* Fix self references when environment variables exist (anujkumar93) [219]

* Fix JSON and HOCON string escaping (dtarakanov1) [209]

* Add samples to MANIFEST.in/sdist (chreekat) [203]
* Use std json library to fix json string escaping (bdmartin) [202]

* Added partial implementation of hocon duration and period recommended api (gabis-precog) [199]

* Do not unquote keys containing special characters (Tommassino) [198]