Updated vagrantfile and readme

I updated the readme to hopefully help new users, which may not understand the relationship of Vagrant and Chef.  I also removed max_retried and timeout since those appear to be deprecated attributes in Vagrant 1.3.5, and their presence caused vagrant up to fail

```shell
jdyer@retina:~/Projects/metasploit(master○) » vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
There are errors in the configuration of this machine. Please fix
the following errors and try again:

SSH:
* The following settings shouldn't exist: max_tries, timeout


```