Find the shortest path.

Building on assignment 3:

Implement a shortest path algorithm to work on the data in the intersections
and connections files.

You do not need to use a heap, but you do need to use a priority queue of
some kind.

Allow the user to enter two intersection numbers,
find the shortest path from the first to the second,
print out step-by-step driving directions listing 
   each segment of road to be followed,
   how long that segment is,
   the segment's approximate direction.

for example:

from intersection 19321 take US-22 3.5 miles W to intersection 19417
from intersection 19417 take US-217 5.2 miles SW to intersection 19392
from intersection 19392 take ME-19 1.7 miles S to intersection 19210

and so on. This sample is not an actual shortest path; it is just to
suggest a neat and tidy output format to you.