Always print the internal representation of the program when requested

Fixes #304. We should always print the internal representation of the program when requested by a command line flag, even if a cached representation of the elm program exists.

Note that this fix causes the elm program to be recompiled whenever the `--print-program` option is given. The other option to fix this bug would have been to store the internal representation, but that seems like too much cost without having a clear benefit.