Don't recommend users use --no-check-certificate

This doesn't serve a useful purpose in a correctly-configred enviroment, even the default one. 

closes #2
Don't run wget as root if we don't need to

Since the second invocation is writing to a local file, having it be root-owned is actually suboptimal since the user would need to `sudo rm` to remove it.
Install shuttle in /usr/local/bin

It isn't a distro-installed application, so put it in `/usr/local/bin as FHS intended.

See http://www.pathname.com/fhs/pub/fhs-2.3.html#USRLOCALLOCALHIERARCHY
Merge pull request #3 from lfaraone/patch-1

Install fixes