This is a fork of @mshanemc 's original lightning sharing component. This is a HEAVILY modified version designed to work better with Salesforce1 mobile and provide better code compartimentization.
Lightning Components Apex to implement adhoc sharing in Lightning Experience Lightning Components + Apex to implement adhoc sharing in Lightning Experience
Clone the project and install the components and apex classes into your org.
Create a lightning quick action on the object you want to share and give it a height of 500px. Place it on the appropriate page layouts under Salesforce1 and Lightning Experience actions.
The component will now be ready to use.