Sentinel-value

Feature
* Reverse parameters of SentinelValue() constructor ([`0a3b77f`](https://github.com/vdmit11/sentinel-value/commit/0a3b77f624f8da0909130381b0a6c5aa9f92e12e))

Breaking
* SentinelValue() parameter order is different now: ([`0a3b77f`](https://github.com/vdmit11/sentinel-value/commit/0a3b77f624f8da0909130381b0a6c5aa9f92e12e))

Fix
* Py.typed is installed to site-packages directory ([`ffa8256`](https://github.com/vdmit11/sentinel-value/commit/ffa8256c02cf691241dee979a3e38be387206b6d))

Fix
* Missing py.typed marker file (see PEP 561) ([`c5bcd5a`](https://github.com/vdmit11/sentinel-value/commit/c5bcd5a5ce1154a2312701469b16fa4831b73494))

Feature
* Initial stable release, remove under-development warning ([`92f1f6f`](https://github.com/vdmit11/sentinel-value/commit/92f1f6f5ad81bd26af4c29c861608f8ffcccc814))