Added command 'git flow log'
install git-flow-log
use base branch instead, if base not found, use master branch
added git flow log usage instructions
Update changelog
Update of the contributers.
Version bump 1.8.0-dev.49
Merge branch 'feature/add-log-command' into develop
Version bump 1.8.0-rc.1
Version bump 1.8.0
Merge branch 'release/1.8.0'
Merge tag '1.8.0' into develop

v1.8.0
Preparation for new development cycle after release 1.8.0