Rec changes

Shuffled around content and rewrote the bitwise operator section for recitation 2. Check out the rec_changes branch for a readable version if you don't want to just check the diffs. Proposed recitation teaching plan for the next few weeks:

- recitation 2: makefiles, bitwise operators, git
- recitation 3: basic c (data types, expressions, statements)
- recitation 4: memory! (pointers, arrays, heap)

cc @jrbalsano & @chmullig for merge