Add features & change usage of random-phrase:

* # words is now the only positional argument
* --senteces flag sets # sentences
* --simple flag disallows capital letters and apostrophes
Forward ports and share volume with transmission.
Refactor transmission docker config.

Details:
* Mount transmission config directory as volume on container. This way,
  the resume/ and torrents/ dirs persist across container restarts. (You
  could use a data-only container for the config directory, if you
  like.)
* Put all transmission data in /transmission in the container.
* Specify a restart policy by passing --restart=always in run.sh.
* Update README.