services/letter/{letter}
Retrieves all of the services that begin with the given letter.
Arguments:
- api_key (required)
 - per_page (optional - default 25)
 - page (optional - default 1)
 - letter (required)
 
Example request:
http://[domain]/api/services/letter/a.xml?api_key=[api_key]
    &per_page=10&page=1&letter=A
Example response:
<?xml version="1.0" encoding="utf-8"?>
<services letter="a" page="1" pages="1" per_page="10" total="2">
    <service id="1">
        <title>Abandoned bicycles</title>
        <eligibility>Eligibility</eligibility>
        <accessibility>Accessibility</accessibility>
        <availability>Availability</availability>
        <content><![CDATA[<p>Abandoned Vehicles</p>]]></content>
        <contacts/>
        <categories>
                <category id="20000" name="Category One"/>
        </categories>
    </service>
    <service id="2">
        <title>Abandoned miscellaneous</title>
        <eligibility>Eligibility</eligibility>
        <accessibility>Accessibility</accessibility>
        <availability>Availability</availability>
        <content>
            <![CDATA[<p>Primary Service content here...</p>]]>
        </content>
        <contacts/>
        <categories>
                <category id="20000" name="Category One"/>
        </categories>
    </service>
</services>