According to this page on the Lightning Design System, the unmanaged package has been deprecated due to SLDS being available in Salesforce without need for a static resource. However, I’m having trouble grabbing SLDS icons for use in lightning components still.
Are the SLDS icons available without the need for a static resource? If so, what’s the path I should use for the SVG?
They are not natively available in lightning. You will need to get a static resource. There is a great explanation on why and the component workaround that you can use until it is supported.
Since posting, lightning components can now extend SLDS by using the force:slds markup.
Lightning Icons can then be used by using the lightning:icon markup: