Merge pull request #173 from twheel/upstream

More helpful error message when ZipInstaller fails
Designer app remembers the tab you were on last
Merge branch 'master' of github.com:jbroadway/elefant
Designer should recognize CSS files in subfolders of theme folders
Added session_domain setting so sessions can work across subdomains
Added session_duration setting to control session expiry length
Updated instructions in config
Fixed fatal error in translator add handler, closes #174
Select multiple files at once from filebrowser