README.md : Document Requirements and Custom events (saycheese, &etc.)

from pull request #12 – 3d6ea411e63a – saycheese
.travis.yml Remove JRuby 1.8 mode from travis builds.  1.8 not supported
Minor version bump:  Add support for Custom Events “shutterbug-saycheese”

From 3d6ea411e63a : pull request #12 “saycheese”