Link Helper

As per issue #30 I thought it would be useful to add a helper for links.

For example, to place the icon-upload-alt icon next to Edit write something like:

`<%= ilink_to "upload-alt", "Edit", edit_post_path(post), class: 'btn btn-mini' %>`

or to place icon-trash next to text Destroy button write:

`<%= ilink_to "trash", "Destroy", post, confirm: 'Are you sure?', method: :delete, class: 'btn btn-mini btn-danger'%>`

(precede the link text with the icon name stripped off icon- prefix)