console command names should support underscore rather than dash

[lsmith77]

haven't used the bundle yet, but from the docs using dash as a separator in the console commands seems like a somewhat un-Symfony2 choice where underscores are preferred for this (see the sandbox). also i wonder if it will work if i put the console script in a non standard location like app/main/console?

then again i should probably just try this out and figure it out myself and send a pull .. oh time how i could use more of you :)

[bobthecow]

Add instructions for alternate executable names.

Added instructions to README for enabling console completion for other executable names. Closed by 11c0396