Splice ./universe directory into ./

Manually merging:
- README.md: I added the description from universe/README.md into the heading of
  dotfiles/README.md.
- .envrc: dotfiles/.envrc was a superset of universe/.envrc
- .gitignore: Adding some of the ignored patterns from universe/.gitignore to
  dotfiles/.gitignore

Everything else here should be a simple rename.

universe/data_structures_and_algorithms/array-traversals.py

@@ -1,87 +0,0 @@
-# This is practice for various types of list traversals that turn up.
-
-xs = range(10)
-n = len(xs)
-
-print('---')
-# pythonic left-to-right traversal
-result = ''
-for x in xs:
-    result += str(x)
-print(result)
-
-print('---')
-# left-to-right traversal
-result = ''
-for i in range(n):
-    result += str(xs[i])
-print(result)
-
-print('---')
-# right-to-left traversal
-result = ''
-for i in range(n):
-    result += str(xs[n - 1 - i])
-print(result)
-
-print('---')
-# 2x left-to-right traversal
-result = ''
-for i in range(2 * n):
-    result += str(xs[i % n])
-print(result)
-
-print('---')
-# 2x right-to-left traversal
-result = ''
-for i in range(2 * n):
-    result += str(xs[(n - 1 - i) % n])
-print(result)
-
-################################################################################
-# Table traversals
-################################################################################
-
-table = [[row * 10 + i for i in range(10)] for row in range(3)]
-row_ct = len(table)
-col_ct = len(table[0])
-
-print('---')
-# 3x10 table traversal
-result = ''
-for row in table:
-    r = ''
-    for col in row:
-        r += '{:3d}'.format(col)
-    result += r + '\n'
-print(result[0:-1])
-
-print('---')
-# 3x10 table traversal
-result = ''
-for row in range(row_ct):
-    r = ''
-    for col in range(col_ct):
-        r += '{:3d}'.format(table[row][col])
-    result += r + '\n'
-print(result[0:-1])
-
-print('---')
-# 3x10 table traversal (reverse)
-result = ''
-for row in range(row_ct):
-    r = ''
-    for col in range(col_ct):
-        r += '{:3d}'.format(table[row_ct - 1 - row][col_ct - 1 - col])
-    result += r + '\n'
-print(result)
-
-print('---')
-# 3x10 column-row traversal
-result = ''
-for col in range(col_ct):
-    r = ''
-    for row in range(row_ct):
-        r += '{:3d}'.format(table[row][col])
-    result += r + '\n'
-print(result)