create new trips
removed manage_trip folder
show trip participants
manage trip participants
protect trip from edit or delete by other users
add POI to trips
one POI can only belong to one trip
UI tweaks
Merge branch 'feature/manage-trips' into develop
adapt to heroku
Merge branch 'release/0.1' into develop
changed back to sqlite3
Merge branch 'release/0.2' into develop
removed vote from POI model
finished part 1
Merge branch 'feature/vote-poi' into develop