flag touchstart event handlers as passive: false

[dannywieser]

Not a critical issue, but when the svg.select.js library is used in an app, chrome outputs several warnings to the console when an SVG element is selected:

[Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event. Consider marking event handler as 'passive' to make the page more responsive. See https://www.chromestatus.com/feature/5745543795965952

Taking a look at the code it appears that the different touchstart events in the code always trigger preventDefault, so it seems that all of the touchstart events in the library could be flagged as passive: false to eliminate these console warnings.

[Fuzzyma]

Jeah - with that change Chrome broke the web (again) because it wasnt compatible with anything else. When you pass the options in, other browsers take it as a boolean true and all of a sudden you have bound to the capture phase instead of the bubble phase. If you know a check to circumvent these, feel free to create PR :)