more robust way to check tesseract version

better way of checking if the tesseract version is compatible with the
script.
If the required tess version is 3.02.02, and the actual version is 3.03,
the script would have told before that the version is too old, because
303<30202, now it compares 3.03>3.0202
fixes #60

Check if the languages option provided to tesseract (-l) are supported
List supported languages

In case lan is not supported, list the supported languages in the error
message