fix typographical errors and omitted files

These minor changes fix a few errors jekyll threw on `make check`.

    Liquid Exception: Included file '/Users/mike/selik/bc/_includes/invperc/grid/challenges/map-grid.html' not found in _includes/guide-invperc/grid/challenges.html, included in lessons/swc-invperc/tutorial.html

    Liquid Exception: Included file '/Users/mike/selik/bc/_includes/guide-invperc/assembly/title.md' not found in lessons/swc-invperc/tutorial.html

    Liquid Exception: Included file '/Users/mike/selik/bc/_includes/guide-invperc/test/title.md' not found in lessons/swc-invperc/tutorial.html

    Liquid Exception: Included file '/Users/mike/selik/bc/_includes/guide-invperc/profile/objectives.html' not found in lessons/swc-invperc/tutorial.html