Write a Python script that computes the complement 
of a DNA sequence.  In other words, your script should convert all 
A's to T's, C's to G's, G's to C's, and T's to A's. 

The input is one sequence in FASTA format in a file called "dna.txt".

For example if the file contains 

>human
ACCGT

then the output of the program should be TGGCA. Note that your program should work for 
any sequence in this format and not just the given example.

Submit a hardcopy in class on Sept 14th.