* Removed phred_to_prob from the struct Memory. It was not being used.

* Modified the ReadSequence struct. Now it has the starting position (in the chunk) of a char4 array instead of 4 char arrays. Previous char arrays were "qual", "ins", "del", "cont". Current char4 array is "qidc".

* Removed unused #ifdef _WIN32 from some places.

* Removed unused function show_time

* Added some comments