Find the shortest path.

Building on assignment 3:

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

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.