Change "alphanumeric" path in Ubuntu

In the Ubuntu section, the path should be:
cp "./share/configs/alphanumeric" "/usr/share/tesseract-ocr/tessdata/configs/alphanumeric"

instead of:
cp "./share/alphanumeric" "/usr/share/tesseract-ocr/tessdata/configs/alphanumeric"

(/configs directory missing)
Merge pull request #6 from Salamon01/patch-1

Change "alphanumeric" path in Ubuntu