Update `engines` in package.json to Node >=0.10
Update `engines` in package.json to Node >=0.10

This package requires Node.js 0.10+ and the `engines` entry was out of date. This corrects that.

Fixes #78

molant/express-handlebars,edorsey/express-handlebars,blendlabs/express-handlebars,ericf/express-handlebars,michaeljunlove/express-handlebars,mello151/express-handlebars,confuser/express-handlebars,iscarecrow/express-handlebars,jeanpan/express-handlebars,camabeh/express-handlebars,rstr74/express-handlebars,lijanele/express-handlebars