Ryunosuke SATO 69bbe89616 Switch short option of --module-ids from -i to -M
`-i` conflicts with `--optional` option.

```
$ bin/6to5/index.js --help | grep "\-i,"
    -i, --optional [list]        List of optional transformers to enable
    -i, --module-ids             Insert module id in modules
```
2015-02-07 16:37:38 +09:00
..
2015-02-05 14:05:15 +11:00