Added a new field to the model.
Added bootstrap class to invoicedate element before template rendering.
Added the new field into the form. Also changed the last form before vendor section to avoid problems when adding dinamically new invoices.
Changed behaviour on ajax success.
Now if we got answer "no mail in our db" the text is placed as placeholder
rather than text.
Added the new field invoicedate to dynamic form construction.
When Add is clicked the standard operations for other fields are made on our
fresh added field.
Merge pull request #6 from MattBlack85/add_invdate_column

Added invoicedate column to model and updated all relative JS/HTML needed.