print-newline-when-building-releases

- Print a newline when emitting a status message during development
  release builds [obvious fix].

This changes this output:

```
jkakar@rex:~/src/github.com/heroku/keg$ make devrel
rm -rf _rel
==> edown (compile)
==> rebar_lock_deps_plugin (compile)
---- 8< snip 8< ---- 8< snip 8< ---- 8< snip 8< ---- 8< snip 8< ----
===> release successfully created!
Symlinking deps and apps into releasejkakar@rex:~/src/github.com/heroku/keg$
```

to this:

```
jkakar@rex:~/src/github.com/heroku/keg$ make devrel
rm -rf _rel
==> edown (compile)
==> rebar_lock_deps_plugin (compile)
---- 8< snip 8< ---- 8< snip 8< ---- 8< snip 8< ---- 8< snip 8< ----
===> release successfully created!
Symlinking deps and apps into release
jkakar@rex:~/src/github.com/heroku/keg$
```