Don't consider existing choices on initial page

Paypal's use of a Bill Me Later option in addition to the default payment option means that the extension's query for `#funding-mix input[type=radio]` always returns at least 2 elements, causing a premature exit.

**Screenshot:**

![pp_initial](https://f.cloud.github.com/assets/324189/1747671/c318bbe4-6467-11e3-8290-45c26b6b17e7.png)

**HTML for the screenshotted section:**

```html
<div class="reviewInfo">
    <h4>
        Payment method
    </h4>
    <span class="scTrack:main:ec:::review:PaymentMethod">
        <span class="action">
            <span class="buttonAsLink">
                <input type="submit" value="Change" id="funding_select" name="funding_select" class="small">
            </span>
        </span>
    </span>
    <span class="add-gift-card">
        <span class="buttonAsLink">
            <input type="submit" value="Now accepting prepaid gift cards" id="add_cc" name="add_cc" class="small">
        </span>
    </span>
    <div id="fundingMixSection" class="selected">
        <div class="topper"></div>
        <fieldset class="middle inset" id="funding-mix">
            <legend class="accessAid">Payment Method</legend>
            <div class="paymentType">
                <div class="ccNumberLabel" id="">
                    <label for="currentfunding">
                        <input class="bcRadio" type="radio" id="currentfunding" checked name="flag_show_ppc_signup_selected" value="default">
                        Instant Transfer : <Bank> Checking (Confirmed) x-####
                    </label>
                </div>
                <span class="paymentValue" id="2">
                    <span class="amount">
                        $#.## USD
                    </span>
                </span>
            </div>
            <div class="backup-funds clearB small secondary">
                PayPal will use <CardType> XXXX-XXXX-XXXX-#### to fund this transaction if your bank does not have enough funds.
            </div>
        </fieldset>
        <div class="bottomer"></div>
    </div>
    <div id="creditOfferSection" class="notselected">
        <div class="topper"></div>
        <fieldset class="middle offerSelection">
            <legend class="accessAid">Credit Offer</legend>
            <div id="creditOffer" class="clearfix">
                <fieldset class="group">
                    <legend class="accessAid">
                        <span class="accessAid">Payment method</span>
                    </legend>
                    <span class="labels paymentMethod">
                        <span class="label">
                            <span class="accessAid">Payment method</span>
                        </span>
                    </span>
                    <div class="fields">
                        <label for="mpi_offer_selected" class="radio">
                            <input type="radio" id="mpi_offer_selected" name="flag_show_ppc_signup_selected" value="BML">
                            Bill Me Later<sup>®</sup>, a PayPal service
                        </label>
                        <div class="creditOfferBanner">
                            <label for="mpi_offer_selected" class="radio">
                                <a target="_blank" class="bannerImage" href="https://www.billmelater.com/cm/paypal/landers/13ebaybmlBUCKSjkl.html" onclick="PAYPAL.core.openWindow(event, {size: 'l'});">
                                    <img id="offerImage" src="https://www.paypalobjects.com/webstatic/MarketingOperations/NA/NA2013/US/imgBML1213ITAKLEBAY10B1PCORE_428x62.gif" border="0" alt="Get more time to pay by choosing Bill Me Later during PayPal Checkout. Subject to credit approval. See Terms. Apply Now.">
                                </a>
                            </label>
                        </div>
                        <div class="showBlock"></div>
                    </div>
                </fieldset>
                <input type="hidden" id="creditOfferSbmtBtnLabel" name="creditOfferSbmtBtn" value="Sign Up and Continue">
            </div>
        </fieldset>
        <div class="bottomer"></div>
    </div>
    <div class="clearFix inset">
        <div class="viewPolicies">
            View <a target="_blank" href="https://www.paypal.com/us/cgi-bin/merchantpaymentweb?cmd=xpt/cps/popup/FundingMixEducation" onclick="PAYPAL.core.openWindow(event, {size:'l'});">PayPal policies</a> and your payment method rights.
        </div>
    </div>
</div>
```