Write a Python script that prints the contents of a file called dna.txt 
in reverse order. For example if the file contains 

>human
ACCGT
>chimp
ACGGT

then the output of the program should be similar to

ACGGT
>chimp
ACCGT
>human

It doesn't have to be exactly like the above but the contents should
appear in reverse order. This means the first sequence should be the
last and the second should be the second last and so forth. The file 
may contain more than two sequences. 

Submit a hardcopy solution in class on Sept 17th.