Added curl support and one test

Now it checks for the existance of curl after
failing to find wget.

Note that I ended up removing the quotes around $url
when referencing it in the call to wget, since urls can't have spaces
anyways, and the correct quoting was messy.

To test, I did

    rm -r .deps
    make clean
    make cmake
    make

And it worked.
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
silence tar when getting libuv