Syntax for filters in resource.list() methods?

Hi @mayconheerdt,

First of all thanks for investing the work to create this NPM package!
Do you know how the syntax for filters in magento.{{resource}}.list() methods works?

Taking the example of magento.customer.list() (http://www.magentocommerce.com/api/soap/customer/customer.list.html), how could I filter for a specific email address? Do you know? Unfortunately, I could not figure it out.
