api/usage.md - Change example fields for `Contact`

The `first_name`/`organiztion_name` is kind of an ugly bit and tangential to
the main point here (entities vs actions vs parameters).  Choose fields that
more clearly apply to all contacts.

docs/api/usage.md

@@ -5,7 +5,7 @@ with the supported actions and parameters:
 
 | Entity                   | Description              | Actions |  Parameters       |
 |--------------------------|--------------------------|---------|-------------------|
-| <code>Contact</code>     | An individual, <br /> organization, or <br />house-hold.         |<code>create</code><br/><code>get</code><br/><code>delete</code><br/>| <code>contact\_type</code><br /> <code>first\_name</code>  <br /><code>last\_name</code> <br /><code>preferred\_language</code>       |
+| <code>Contact</code>     | An individual, <br /> organization, or <br />house-hold.         |<code>create</code><br/><code>get</code><br/><code>delete</code><br/>| <code>contact\_type</code><br /> <code>nick\_name</code>  <br /><code>preferred\_language</code>       |
 | <code>Activity</code>    | An phone call, meeting,<br /> or email message. that <br /> has occurred (or will <br /> occur) at a specific <br /> date and time|<code>create</code><br/><code>get</code><br/><code>delete</code><br/>| <code>activity\_type\_id</code> <br /> <code>source\_contact\_id</code> <br /> <code>assignee\_contact\_id</code>    |
 | <code>Address</code>     | A street-address related <br /> to a contact. |<code>create</code><br/><code>get</code><br/><code>delete</code><br/>| <code>contact\_id</code>,  <br /> <code>street\_address</code> <br /> <code>city</code>  <br /> <code>state\_province\_id</code> <br /> <code>country\_id</code>     |