fix height calculation for box-sizing:border-box with a border
fix height calculation for box-sizing:border-box with a border

this fixes an issue where the height would always be a little too small if
you have a border, resulting in perma-scrollbars in many browsers

incidentally this now also supports box-sizing:padding-box (firefox only)

kakadiya91/react-textarea-autosize,plyo/react-textarea-autosize,jquense/react-textarea-autosize,koistya/react-textarea-autosize,frankychung/react-textarea-autosize,frederickfogerty/react-textarea-autosize,nickpresta/react-textarea-autosize,kakadiya91/react-textarea-autosize,andreypopp/react-textarea-autosize,andreypopp/react-textarea-autosize,jquense/react-textarea-autosize,razh/react-textarea-autosize,nickpresta/react-textarea-autosize,andreypopp/react-textarea-autosize,koistya/react-textarea-autosize,plyo/react-textarea-autosize,frankychung/react-textarea-autosize,razh/react-textarea-autosize,frederickfogerty/react-textarea-autosize