It's not needed since the automatically generated file
SQLiteCppConfig.cmake already exists.
Added a small section to the README to explain how it can be used when
this library is installed to the system.
Fixes#283
Without this, systems that linked against Threads::Threads (namely
Linux) don't "just work" with find_package(SQLiteCpp), but instead
require you to find & link against Threads manually.
So this fixes that by finiding it for you, if it was used.
Add FindSQLite3 from CMake v3.14 in cmake subdir custom CMake modules like FindSQLiteCpp
Add this cmake subdir to CMAKE_MODULE_PATH
Add a Travis CI build configuration using the libsqlite3-dev packagee from the Linux/Ubuntu distribution