[Fix] don't treat cost matrix values as an integer

When we enter float value inside cost matrix, "print_matrix" function
treats those values as integer, and only prints integral part of the
values.

For example, if cost matrix is:
matrix = [[5.1, 9.6, 1.7],
          [10.2, 3.5, 2.8],
          [8.3, 7.4, 4.9]]

Then output is as follows:
Lowest cost through this matrix:
[   5,    9,    1]
[  10,    3,    2]
[   8,    7,    4]
(0, 0) -> 5.1
(1, 1) -> 3.5
(2, 2) -> 4.9
total cost: 13.5

We can see printed cost matrix isn't same as original cost matrix. And
it's not always the case, cost matrix would have all values in integral
form, cost of the assignment could be a float value.

Resolves: bmc#34

munkres.py

@@ -485,7 +485,7 @@ def make_cost_matrix(
 
 def print_matrix(matrix: Matrix, msg: Optional[str] = None) -> None:
     """
-    Convenience function: Displays the contents of a matrix of integers.
+    Convenience function: Displays the contents of a matrix.
 
     **Parameters**
 
@@ -513,8 +513,8 @@ def print_matrix(matrix: Matrix, msg: Optional[str] = None) -> None:
         sep = '['
         for val in row:
             if val is DISALLOWED:
-                formatted = ((format + 's') % DISALLOWED_PRINTVAL)
-            else: formatted = ((format + 'd') % val)
+                val = DISALLOWED_PRINTVAL
+            formatted = ((format + 's') % val)
             sys.stdout.write(sep + formatted)
             sep = ', '
         sys.stdout.write(']\n')