readme: added "Contributing" section
readme: fix database server connection error message
install: store gitlab application logs at `/var/log/gitlab/gitlab/`
install: store gitlab-shell logs at `/var/log/gitlab/gitlab-shell/`
install: store gitlab vhost access logs at `/var/log/gitlab/nginx/`
install: store supervisor logs at `/var/log/gitlab/supervisor/`
dockerfile: added volume mount instruction for `/var/log/gitlab`
changelog: updated
Merge branch 'logs-volume'

Closes #40
init: added SMTP_OPENSSL_VERIFY_MODE configuration option

Refer #179
readme: clean up the "Mail" section
config: fix smtp_settings.rb template
config: whitespace cleanup
install: do not create the ${GITLAB_DATA_DIR}/.ssh directory, its created in the init script
install: do not create the ${GITLAB_DATA_DIR}
Revert "install: do not create the ${GITLAB_DATA_DIR}/.ssh directory, its created in the init script"

This reverts commit 8aba575f89cde29a03cc3537a7f99799ceaf8b07.
Revert "install: do not create the ${GITLAB_DATA_DIR}"

This reverts commit 45edbf3469dd96fd7914a5c10a61a984b77cc2b8.
install: move supervisord.log file to /var/log/redmine/supervisor/
install: move nginx logs to /var/log/gitlab/nginx/
init: cleanup database.yml reconnect option setting