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/shuffle.py

@@ -1,34 +0,0 @@
-import random
-
-
-def get_random(floor, ceiling):
-    return random.randrange(floor, ceiling + 1)
-
-
-# shuffle_in_place :: [a] -> IO ()
-def shuffle_in_place(xs):
-    """Fisher-Yates algorithm. Notice that shuffling here is the same as
-    selecting a random permutation of the input set, `xs`."""
-    n = len(xs) - 1
-    for i in range(len(xs)):
-        r = get_random(i, n)
-        xs[i], xs[r] = xs[r], xs[i]
-    return xs
-
-
-# shuffle :: [a] -> [a]
-def shuffle_not_in_place(xs):
-    result = []
-
-    while xs:
-        i = get_random(0, len(xs) - 1)
-        x = xs.pop(i)
-        result.append(x)
-
-    return result
-
-
-xs = [x for x in range(9)]
-print(xs)
-# print(shuffle_not_in_place(xs))
-print(shuffle_in_place(xs[:]))