Logfile path is converted to an absolute path before processing

This fixes
https://github.com/EqualExperts/opslogger/issues/2

Also add a .gitignore for test files that might get created.
Due to the nature of the tests (paths have to be relative to the
current directory), the test files have to be in an inconvenient
location.
Make the logfile path absolute in the setter
Change version to 0.1.1