Merge pull request #8 from audreyt/master

Tooltip styling
content_script.js, re-styling
content_script.js, prevent $('#moedict-extension') appendTo body every time.
content_script.js, move some local variables to global variables.
content_script.js, add trs2bpmf from moedict-webkit repo
manifest, add icons
styles.css, change some css for extension look
content_script.js, remove jquery-ui class
manifest.json, exclude_matches moedict.org and moedict.tw websites
content_script.js, close $('#moedict-extension') when click document
content_script.js, dirty hack for prevent onmouseup event trigger when clicking
content_script.js, add z-index: 9999 in $('#moedict-extension')