I had this same issue using the RC version and it has just cropped up again for me with the RTM so worth documenting for future reference.
The issue I had was as follows: Installed the default install of Visual Studio, created a new Web App (vNext) and then tried to add angular. It just kept telling me that the package was not installed and I didn’t get any intellisense in dependencies for versions in the bower.json file.
Re-run the VS2015 install, choose modify and make sure the Git and Node options are selected.
Next make sure that “C:\Program Files (x86)\Git\bin” is on your path. It wasn’t by default for me.
And lastly to make sure we can talk to Git to get packages through our firewall run a command prompt from “C:\Program Files (x86)\Git\bin” and execute the following command.
git config –global url.”https://”.insteadOf git://
4 hours saved the 2nd time I had this issue