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 :)
I know that it was there before, but do you have a better suggestion than "sync" here? It made sense before when we were using `syncdb` but not that we've switched to `migrate`, I'm not sure if it does anymore.