upstream changes:
-----------------
Version 1.0.24
* Updating p1_utils to version 1.0.21.
Version 1.0.23
* Exclude old OTP releases from Travis
* Fix hex to support compiling ejabberd with rebar3
Version 1.0.22
* Updating p1_utils to version 1.0.20.
Version 1.0.21
* Fix compilation with Erlang/OTP 23.0, and Travis
Version 1.0.20
* Updating p1_utils to version 1.0.19.
Version 1.0.19
* Updating p1_utils to version 1.0.18.
* Update copyright year
Version 1.0.18
* Updating p1_utils to version 1.0.17.
Version 1.0.17
* Updating p1_utils to version 1.0.16.
Version 1.0.16
* Updating p1_utils to version 1.0.15.
Version 1.0.15
* Updating p1_utils to version 1.0.14.
* Add contribution guide
* Fix license discrepancies
Version 1.0.14
* Updating p1_utils to version 1.0.13.
Version 1.0.13
* Updating p1_utils to version 6ff85e8.
f22556f287