Check if file is PDF by magic number. Closes #98
Check if file is PDF by magic number. Closes #98

See http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/pdf/pdfs/pdf_reference_1-7.pdf page 92

ebp/docsplit,jurek7/docsplit,jurek7/docsplit,ebp/docsplit