Added 'C', fixed 'D' shift from turtle position

First I realized the grid was offset one block for every letter after the D on the
proof so I modified the turtle's final position to correctly be the lower-left corner.

I mapped the 'C' and was proud at how smoothly it worked on the test.py run until I
ran proof.py and the whole thing went crazy. Turns out while I had noted all of the
segment lengths and angles for the turns, I can't tell right from left and ended up
shifting 135 degrees in the wrong direction, which explained the crazy. If I was feeling
anything there, it would be the embodiment of "oh no, what now?"

typeface.py

@@ -34,10 +34,38 @@ def draw_letter_b(unit):
     pass
 
 def draw_letter_c(unit):
-    pass
+    no_pen(3,unit)
+
+    segment(4,unit)
+    left(90)
+    segment(2,unit)
+    left(90)
+    segment(2,unit)
+    right(45)
+    diagonal(2,unit)
+    right(90)
+    diagonal(2,unit)
+    right(45)
+    segment(2,unit)
+    left(90)
+    segment(2,unit)
+    left(90)
+    segment(4,unit)
+    left(45)
+    diagonal(2,unit)
+    left(45)
+    segment(4,unit)
+    left(45)
+    diagonal(2,unit)
+
+    right(135)
+    no_pen(3,unit)
+    left(180)
 
 def draw_letter_d(unit):
     no_pen(1,unit)
+
+    # the outline of the D
     segment(5,unit)
     left(45)
     diagonal(1,unit)
@@ -49,10 +77,13 @@ def draw_letter_d(unit):
     segment(5,unit)
     left(90)
     segment(8,unit)
+
     left(90)
     no_pen(2,unit)
     left(90)
     no_pen(2,unit)
+
+    # the inner part of the D
     segment(4,unit)
     right(90)
     segment(1,unit)
@@ -64,7 +95,8 @@ def draw_letter_d(unit):
     diagonal(1,unit)
     right(45)
     segment(1,unit)
-    no_pen(2,unit)
+
+    no_pen(3,unit)
     left(90)
     no_pen(2,unit)
     left(90)