Merge pull request #11 from ayr0/arrayprobs

corrections and fixes
Revised solutions for Arrays lab
Typo fixes in Arrays lab and redid array_solutions.py
Removed a stray image alloc_vs_resize.pdf that was in the folder for the
arrays lab. Also added a brief warning to avoid appending to arrays to
that lab.
Consolidated problems in the arrays lab
Sleight change in order of arrays lab.
Fixed some typos in the arrays lab.
tidy up solutions.