Update Vagrant download url to 1.4.3 - #19

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Bump version to 1.4.3 in vagrant.nuspec - #19

Fix #19: Update Vagrant to 1.4.3

Signed-off-by: Rogerio Prado de Jesus <rogeriopradoj@gmail.com>
Merge pull request #20 from rogeriopradoj/fix-19

Fix #19: Update Vagrant to 1.4.3