Fix typo ("every day" to "everyday") in 2013-04
Day 01 of 2013-05 challenge

Update main README file with an entry for 2013-05 challenge, create a
directory for 2013-05 challenge and add the following files in it:
    1. README file for 2013-05 challenge with content for day 01
    2. Source code for a scene with balls and boxes
    3. Image rendered by POV-Ray
    4. POV-Ray binary installer for Linux