Update task to add methods_only parameter

[jomontanari]

I want to use flog in my build with the rake task and set a max score per method, but it's currently failing because main#none has a ridiculously high score.

I found that I can use the flag -m on the command line but it wasn't available from the rake task. I've just added a parameter defaulted to false, seemed the simplest thing but let me know if you have a better suggestion.

[zenspider]

Not a biggie on a diff this small, but next time do the additions in one commit and the reformatting in another.

[zenspider]

Merged. Thanks!