Log Message:
py-lz4: updated to 2.1.5

2.1.5
This release contains no functional changes other than changes to the Appveyor \ 
configuration for publishing wheels.

2.1.4
This release contains no functional changes other than changes to the Travis \ 
configuration for publishing wheels.

2.1.3
A simplification of the tox.ini file
More robust checking for pkgconfig availability
Integration of cibuildwheel into travis builds so as to build and publish binary \ 
wheels for Linux and OSX
Only require pytest-runner if pytest/test is being called
Blacklists version 3.3.0 of pytest which has a bug that can cause the tests to fail.