Release checklist

Update version number in

include/lsl_c.h, LSL_COMPILE_HEADER_VERSION
CMakeLists.txt in project()
src/common.h, LSL_LIBRARY_VERSION
.appveyor.yml, version and deploy.version

Build binaries:

Appveyor: Windows x86, x64, Ubuntu 16.04 x64, 18.04 x64
Travis: Ubuntu 14.04 x64, OS X x64