Now that we have a nice [HTML view of all nightly builds][nightlies],
let's link to them!

[nightlies]: https://ci.riot-os.org/nightlies.html#master

With some minor hand-edits I used the following chain of commands:

```sh
git rm sys/include/net/gnrc/netdev.h
git grep --name-only -i netdev2 | \
        xargs sed -i -e 's/^\(NETDEV\)2\(.*\)\( [("]\)/\1\2 \3/g' \
                     -e 's/\(netdev\)2\(.*\)\( \/\*\*<\)/\1\2 \3/I' \
                     -e 's/\(netdev\)2/\1/gI'
git add -p
git commit --amend
git ls-tree --full-tree -r HEAD --name-only | \
        grep "netdev2" | xargs -I'{}' dirname '{}' | uniq | \
        grep "netdev2" | while read dir; do
                new_dir="$(echo "$dir" | sed "s/netdev2/netdev/g")"
                git mv -f "$dir" "$new_dir"
        done
git commit --amend
git ls-tree --full-tree -r HEAD --name-only | \
        grep "netdev2" | while read file; do
                new_file="$(echo "$file" | sed "s/netdev2/netdev/g")"
                git mv -f "$file" "$new_file"
        done
git commit --amend
git grep --name-only "\<drivers_netdev_netdev\>" | \
        xargs sed -i "s/\<drivers_netdev_netdev\>/drivers_netdev_api/g"
git add -p
git commit --amend
```

addressed comments

wordsmithing around non-viral term

Used some reworked umbrella text from latest release notes to provide more synthetic information upfront (as this README is the first thing people read on GitHub).