Adds explicit check for file format.
If the user specifies hmmer_text and the file is e.g. domtab, the biopython parser will just not yield any lines.
This causes the number of cazyme counts to be all zero.
I've added explicit checks to make sure that the format is correct and checks for zero-count files to warn people or raise an error if the format appears to be wrong.
Also added google colab link to make things marginally easier.