revisions to Deploy chapter

Based on @judy2k's feedback from Django Girls Amsterdam - his group had some problems with the end of the Deploy chapter, where they saw an error message when they first open the app after deploying - the error was mentioned but not very clearly, and caused some confusion.  I also made some English edits again to the beginning section :)
Done - just referred back to what we had to do in the "start project" chapter instead - see what you think :)