Workspace structure is now GOPATH compatile

the original version was a self sustained project
but did not work well with other dependencies
or projects.
Now any user can use this project with
go get github.com/VoycerAG/gridfs-image-server
Update travis configuration for new workspace structure
Update readme travis icon for branch
Add linux binary and new cross compile script
Readme.md prepared for master
Merge pull request #2 from VoycerAG/feature/GOPATH

This project is now $GOPATH compatible.