beginning work on invoice generator
add logo
add from address
add to address
put box around to address
draw project name
draw 'Invoice' at top
center 'Project' label
drawing boxes for invoice info
adding content for invoice info box
fix address formatting when fields are missing
draw outline of line items table
display line items
assuming that not more than 16 line items are invoiced
start on footer
re-position footer box
add total to invoice
implement footer text
inches helper function
fix InvoicePdf.generate_pdf