Introduced package for tests and added a test case for str_to_sprite.

The string variant of the "one-up" image, however, does not match the number-based one, to the expectation for the test had to be adjusted (basically replacing 1s with 0s).

tests/test_str_to_sprite.py

@@ -0,0 +1,27 @@
+from gitfiti import str_to_sprite, ONEUP_STR
+
+
+SYMBOLS = '''
+ ******* 
+*=~~-~~=*
+*~~---~~*
+*=*****=*
+**-*-*-**
+ *-----* 
+  *****  
+'''
+
+NUMBERS = [
+  [0,4,4,4,4,4,4,4,0],
+  [4,3,2,2,0,2,2,3,4],
+  [4,2,2,0,0,0,2,2,4],
+  [4,3,4,4,4,4,4,3,4],
+  [4,4,0,4,0,4,0,4,4],
+  [0,4,0,0,0,0,0,4,0],
+  [0,0,4,4,4,4,4,0,0],
+]
+
+
+def test_symbols_to_numbers():
+    actual = str_to_sprite(SYMBOLS)
+    assert actual == NUMBERS