Vagrant test environment

This Vagrant file spins up two virtual servers (named 'server0' and
'server1') on 'vagrant up' with the minimum prerequisites needed to run
Build.PL.

Fix stupid typo in the docs
Added prefix 'FileSync/' before paths with 'SyncDiff' folder in MANIFEST file to fix missing file warnings on running Build.PL
Basic Travis-CI config
Add librsync-dev to Travis install
Move librsync-dev to Travis before_install