Add meta tag with charset information to application layout.
Previously, our default HTML would validate properly, but would generate a warning: it doesn't declare a character encoding. According to [the spec][encoding-spec], if you don't specify an encoding, a 7 step algorithm happens, with a toooon of sub-steps. Or, we could just actually specify it. Since everything else in Rails assumes UTF-8, we should make sure pages are served with that encoding too. This meta tag is the simplest way to accomplish this. More resources: * http://blog.whatwg.org/the-road-to-html-5-character-encoding * http://www.w3.org/International/tutorials/tutorial-char-enc/ * http://validator.w3.org/ [encoding-spec]: http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#determining-the-character-encoding