Silence wget

Silenced wget's progress bar

This way it won't show up in travis-ci like:

    0% [                                       ] 0           --.-K/s
    100%[======================================>] 371,453     --.-K/s

interleaved with the rest of the output.

This builds off of #61, but it is logically a separate fix.  I'm not sure what the proper etiquette is in terms of github pull requests.