Added .gitignore file

Signed-off-by: David Parry-Smith <david.parry-smith@sanger.ac.uk>
Amended documentation for the search_seq_mismatch method

Signed-off-by: David Parry-Smith <david.parry-smith@sanger.ac.uk>
Implemented search_mismatches and supporting methods

Deals with large files by processing a line at a time
and merging the results
Added title and progress indication