0.15.0

• Update callbacks to pass element per docs (@kpdecker)
• preserve options (@fb55)
• Use SVG travis badge (@t3chnoboy)
• only use static requires (@fb55)
• Optimize manipulation methods (@kpdecker)
• Optimize add and remove class cases (@kpdecker)
• accept dom of DomHandler to cheerio.load (@nleush)
• added parentsUntil method (@finspin)
• Add performance optimization and bug fix empty method (@kpdecker)