Updated hw4-contributing/README.md
Updated README.md files in assignments to include test script instructions.
Merge pull request #479 from jfan013/cs100-2014fall

Fixed typo and added a line for readability
Merge pull request #490 from gbrlrz017/cs100-2014fall

Updated README.md files in assignments to include test script instructions.
Merge remote-tracking branch 'upstream/cs100-2014fall' into cs100-2014fall
removed a broken picture in shell-tricks