Adds documentation to the website. Explains how to format the time.

website/source/docs/templates/configuration-templates.html.markdown

@@ -55,9 +55,62 @@ in Packer templates. These are listed below for reference.
 
 * `pwd` - The working directory while executing Packer.
 * `isotime` - UTC time in RFC-3339 format.
+* <code>isotime &#96;&lt;format&gt;&#96;</code> - UTC time in [&lt;format&gt;](http://golang.org/pkg/time/#example_Time_Format) format.
 * `timestamp` - The current Unix timestamp in UTC.
 * `uuid` - Returns a random UUID.
 
+### isotime Format
+Formatting for the function <code>isotime &#96;&lt;format&gt;&#96;</code> uses the magic reference date **Mon Jan 2 15:04:05 -0700 MST 2006**, which breaks down to the following:
+
+ <table border="1" cellpadding="5" width="100%">
+ 	<tr bgcolor="lightgray">
+ 		<td></td>
+ 		<td align="center"><strong>Day of Week</strong></td>
+ 		<td align="center"><strong>Month</strong></td>
+ 		<td align="center"><strong>Date</strong></td>
+ 		<td align="center"><strong>Hour</strong></td>
+ 		<td align="center"><strong>Minute</strong></td>
+ 		<td align="center"><strong>Second</strong></td>
+ 		<td align="center"><strong>Year</strong></td>
+ 		<td align="center"><strong>Timezone</strong></td>
+ 	</tr>
+ 	<tr>
+ 		<td><strong>Numeric</strong></td>
+ 		<td align="center">-</td>
+ 		<td align="center">01</td>
+ 		<td align="center">02</td>
+ 		<td align="center">03 (15)</td>
+ 		<td align="center">04</td>
+ 		<td align="center">05</td>
+ 		<td align="center">06</td>
+ 		<td align="center">-0700</td>
+ 	</tr>
+ 	<tr>
+ 		<td><strong>Textual</strong></td>
+ 		<td align="center">Monday (Mon)</td>
+ 		<td align="center">January (Jan)</td>
+ 		<td align="center">-</td>
+ 		<td align="center">-</td>
+ 		<td align="center">-</td>
+ 		<td align="center">-</td>
+ 		<td align="center">-</td>
+ 		<td align="center">MST</td>
+ 	</tr>
+ </table>
+ _The values in parentheses are the abbreviated, or 24-hour clock values_
+ 
+ Here are some example formated time, using the above format options:
+ 
+ <pre>
+isotime = June 7, 7:22:43pm 2014
+
+{{isotime "2006-01-02"}} = 2014-06-07
+{{isotime "Mon 1506"}} = Sat 1914
+{{isotime "01-Jan-06 03\_04\_05"}} = 07-Jun-2014 07\_22\_43
+{{isotime "Hour15Year200603"}} = Hour19Year201407
+</pre>
+
+
 ## Amazon Specific Functions
 
 Specific to Amazon builders: