Update DevelopersInformation.md

Added some information about git stash.
Merge pull request #45 from FreekDB/master

ReportPDFExporter: fixed several Checkstyle and other small issues.
Update DevelopersInformation.md

Some small changes.
Update DevelopersInformation.md
Update DevelopersInformation.md

Added a remark for FindBugs: compile before running it.
Added Travis CI configuration file