Error compiling Google Analytics plugin

I am trying to implement Google Analytics into my project. I imported the googleanalyticsv3.unitypackage plugin, but when I tried building it, it failed and gave me this error:

D:\Projects\Unity\Queue\Assets\Plugins\Editor\RangedTooltipDrawer.js(17,17): Error BCE0018: The name 'RangedTooltipAttribute' does not denote a valid type ('not found'). (BCE0018) (Assembly-UnityScript-Editor-firstpass)

The funny thing is, when I tried importing it to a new empty project, it worked. No compile error at all. Any idea why this is?

Thanks in advance.