Fetch Image URL from entry CMS
I bet this trips up a lot of people at first, but your asset field will return a ElementCriteriaModel, not your image.

To get to image, you need to fetch it. If your field has only one image, you will do something like this:

{# Fetches the first image #}
{% set image = entry.featureImage.first() %}
{# It's good to check if you actually have an image before trying to get the url #}
{% if image %}
    {{ image.url }}
    {# Or alternatively #}
    {{ image.getUrl() }}
    {# If you want to get a specific transform: #}
    {{ image.getUrl('transformHandle') }}
{% endif %}


The Assets fields documentation got some good examples on the different use cases.