Write a Python script that counts the number of A's, C's, G's,
and T's in the data given below. Assume that each sequence 
contains just one nucleotide. Use a dictionary with keys
A, C, G, and T, and values as counts of each nucleotide.

For example if the input in the file dna.txt is

>human
A
>mouse
A
>cat
T
>dog
A
>rat
C
>sheep
C
>cow
A

then your program should output

{ 'A':4 , 'C':2, 'G':0, 'T':1 }

Your program should work for any number of sequences and not just 7
as shown above. 

Submit a hardcopy in class on Oct 25th.