changed variable name filepath to file_path in README.rst

[Atishaysjain]

In readme file the variable file_path is defined as:

file_path = './snap_gene_file.dna'

But while passing that variable as an argument into the function snapgene_file_to_dict and snapgene_file_to_seqrecord it is misnamed as filepath:

dictionnary = snapgene_file_to_dict(filepath)
seqrecord = snapgene_file_to_seqrecord(filepath)

Thus the above two lines have been updated to:

dictionnary = snapgene_file_to_dict(file_path)
seqrecord = snapgene_file_to_seqrecord(file_path)

[veghp]

Thank you. This will be part of the next release.