Add empty-var and empty-var-unset integration test
Add TestEnvDiffEmptyValue
Fix issue #114 - work for blank envs
Merge pull request #115 from zimbatm/issue-114

Fix issue #114 - work for blank envs
Bump command timeout to 5 seconds
Allow to disable logging by setting an empty DIRENV_LOG_FORMAT

`export DIRENV_LOG_FORMAT` to disable direnv logging
Log output consistency
Fixes ruby deprecation warning
Fixes `make install` to not create a ./bin directory
replace ronn by md2man

ronn is unmaintained since 2 years and it's dependency, hpricot doesn't
install anymore on ruby2+ on OSX.

Both suffer from the bug described in #113 but at least md2man is going to
be fixed. See sunaku/md2man#18
Doc updates