Tidy up structure of briefcase

I had a spare fifteen minutes and decided that I should tidy up my
monorepo. The work of tidying up is not finished; this is a small step in the
right direction.

TL;DR
- Created a tools directory
- Created a scratch directory (see README.md for more information)
- Added README.md to third_party
- Renamed delete_dotfile_symlinks -> symlinkManager
- Packaged symlinkManager as an executable symlink-mgr using buildGo

data_structures_and_algorithms/highest-product-of-3.py

@@ -1,89 +0,0 @@
-import unittest
-
-
-################################################################################
-# Solution
-################################################################################
-# f :: [Int] -> Int
-def highest_product_of_3(xs):
-    """Here we're greedily storing:
-    - current max
-    - largest product of two
-    - largest positive number
-    - second largest positive number
-    - largest negative number
-    """
-    if len(xs) < 3:
-        raise Exception
-
-    cm = None
-    ld = xs[0] * xs[1]
-    l2 = min(xs[0], xs[1])
-    if xs[0] < 0 or xs[1] < 0:
-        ln = min(xs[0], xs[1])
-    else:
-        ln = 1
-    l = max(xs[0], xs[1])
-
-    for x in xs[2:]:
-        if not cm:
-            cm = max(x * ln * l, ld * x, x * l * l2)  # beware
-            ld = max(ld, x * ln, x * l)
-            ln = min(ln, x)
-            l = max(l, x)
-            if x < l:
-                l2 = max(l2, x)
-        else:
-            cm = max(cm, x * ln * l, x * ld, x * l * l2)
-            ld = max(ld, x * ln, x * l)
-            ln = min(ln, x)
-            l = max(l, x)
-            if x < l:
-                l2 = max(l2, x)
-
-    return cm
-
-
-################################################################################
-# Tests
-################################################################################
-class Test(unittest.TestCase):
-    def test_short_list(self):
-        actual = highest_product_of_3([1, 2, 3, 4])
-        expected = 24
-        self.assertEqual(actual, expected)
-
-    def test_longer_list(self):
-        actual = highest_product_of_3([6, 1, 3, 5, 7, 8, 2])
-        expected = 336
-        self.assertEqual(actual, expected)
-
-    def test_list_has_one_negative(self):
-        actual = highest_product_of_3([-5, 4, 8, 2, 3])
-        expected = 96
-        self.assertEqual(actual, expected)
-
-    def test_list_has_two_negatives(self):
-        actual = highest_product_of_3([-10, 1, 3, 2, -10])
-        expected = 300
-        self.assertEqual(actual, expected)
-
-    def test_list_is_all_negatives(self):
-        actual = highest_product_of_3([-5, -1, -3, -2])
-        expected = -6
-        self.assertEqual(actual, expected)
-
-    def test_error_with_empty_list(self):
-        with self.assertRaises(Exception):
-            highest_product_of_3([])
-
-    def test_error_with_one_number(self):
-        with self.assertRaises(Exception):
-            highest_product_of_3([1])
-
-    def test_error_with_two_numbers(self):
-        with self.assertRaises(Exception):
-            highest_product_of_3([1, 1])
-
-
-unittest.main(verbosity=2)