Handle errors from gopdfi lib

Updated gopdfi version

We are closed, v2

Merge oliverpool's out-of-range rune check

Merge benoitkugler's modification time pull request

We are closed

Merge branch 'oliverpool-master'

Merge branch 'benoitkugler-master'

Address issue jung-kurt#333 by removing at most one trailing newline …

…from txtStr in MultiCell() with non-UTF-8 fonts only. Explain this in MultiCell() documentation.

Merge Benoit KUGLER's support for file attachments and annotations