Add coding exercises for Facebook interviews

Add attempts at solving coding problems to Briefcase.

scratch/facebook/linked_list.py

@@ -0,0 +1,22 @@
+class Node(object):
+    def __init__(self, value=None, next=None):
+        self.value = value
+        self.next = next
+
+    def __repr__(self):
+        result = []
+        node = self
+        while node:
+            result.append(str(node.value))
+            node = node.next
+        return 'LinkedList({xs})'.format(xs=', '.join(result))
+
+def from_list(xs):
+    head = Node(xs[0])
+    node = head
+    for x in xs[1:]:
+        node.next = Node(x)
+        node = node.next
+    return head
+
+list = from_list(['A', 'B', 'C'])