Add seekTo mode support

[gosticks]

adds optional seekToMode parameter that allows the behaviour of seekTo to be controlled. This is usefull when controlling the currentTime with subsecond precision and operating in the range between 0..1 seconds. Some additional changes:

• refactored ref to use new syntax (this.refs is deprecated)
• fixed some formatting inconsistencies

If you prefer me to revert the formatting changes just let me know and I will updated the PR. Thanks for your time!