Compile sshfs as part of the build

[ElDeveloper]

We should be compiling sshfs instead of shipping a pre-compiled version, that IIRC came out of OSXFuse. @stewiem2000 already has some code to do this, so perhaps that would be the way to go.

Related to #11.

[pdondl]

For sshfs, what always worked well for me was to simply use the one from the OSXFuse website (sshfs 2.5.0). I am simply replacing the file sshfs-static in the plugin with a symlink to /usr/local/bin/sshfs.