Custom tagname feature via 'tagname' prop

thanks to denwerboy who added the new feature.

fix wrong method names for init and uninit

thanks to lbineau for fixed the bug

support keep-alive and add a props

1. swicher of props, could control the vue-perfect-scrollbar on/off
2. support vue keep-alive.you can try it by run

npm run example:vuerouter

witch vue-router

1. Update index.vue to Added position: relative to .ps-container
2. added name for the component
3. added an example which worked with vueRouter. npm run example:vuerouter

Manual update method

thanks to FlorianRoettges for adding the method of update