Add support for ";", "&&", and "||"

Bash supports the syntax `cmd1;cmd2`, which executes the first command and then executes the second command (it's the same as if these were two different commands). Also, Bash supports `cmd1 && cmd2` (execute the first command, if it succeeds execute the second) and `cmd1 || cmd2` (execute the first command, if it fails execute the second). These would be awesome features to support.

Not sure if this should be handled by vorpal or by cash, but I figured I would post it here since this is the use-case I had in mind.