Mutated characters should be lower case

Might be helpful to add "cigar" string like information about mutation to the read id.

Right now we have something like:

@Lambdaclone23-2:1-9786W:Lambdaclone23-2:5:9786:27:241:A/2

and we might add add something like:

@Lambdaclone23-2:1-9786W:Lambdaclone23-2:5:9786:27:241:1A23T25C17C:A/2

indicating that positions 1, 23, 25 and 17 where mutated from A,T,C, and C.