README out of date

[pdimens]

Good afternoon,

I noticed there are two things in the readme that are not up to date to the current way LRTK is to be used:

1. lrtk needs to invoked as lowercase
2. lrtk MKFQ requires a path to a directory for the -CF input, not the config.txt file itself.

[CicyYeung]

Thanks for pointing out these problems.

1. we replaced the word "LRTK" with "lrtk" in the commands.
2. we corrected the descriptions as "-CF/--config_file: The path to the directory containing config_files for linked-read simulation."