Map does not resize properly on IE11

[TimFau]

Thanks for the plugin! It's been very helpful. One issue I found is that it does not seem to resize properly for IE11.

1. In IE11, go to: https://www.travismclarke.com/imagemap/
2. Resize window to about 800px wide
3. Click on "Orange" shape & see that "Pink" is selected
4. Also try clicking on top left corner of "Yellow shape" & see blue is selected

[clarketm]

Thanks for the issue. 🤔 let me see if this can be polyfilled in the build process.

[clarketm]

@TimFau
I made a few tweaks to the bundle to resolve issues with IE 9, 10, 11.

1. Remove usage on Symbol as it is unknown to IE ('Symbol' is undefined problem in ie11 babel/babel#7597)
2. Bypass image cache for img load event (e.g. https://davidwalsh.name/image-load-event).

v1.1.7 contains the fixes.