New schema for lab machine data

Fixes #6 
Closes #4 


## New Schema

* hostname: the hostname of the machine
* os: "windows" or "linux"
* users: information about the number of users connected to the machine
  * total: the total number of users connected
  * tty: number of users physically at the machine (linux only)
  * pts: number of users ssh'd into the machine (linux only)
* timestamp: the timestamp for when this data was collected

### Examples

<table>
  <thead><tr><td>Windows machine</td><td>Linux machine</td></tr></thead>
  <tbody>
  <tr><td>
<pre>
{
   hostname: "beedrill",
   os: "windows",
   users: {
     total: 21
   },
   timestamp: 1359478515
}
</pre>
</td>
<td>
<pre>
{
   hostname: "majorhavoc",
   os: "linux",
   users: {
     total: 21,
     tty: 1,
     pts: 20
   },
   timestamp: 1359478515
}
</pre>
</td>
</tr>
</tbody>
</table>