Curl -> Tar of remote repo

[nrakochy]

When running these commands -

lein new onyx-app example -- +docker
cd example && lein do clean, uberjar; docker build -t peerimage .

I am getting an error -
cp: can't stat '/tmp/etc/*': No such file or directory

I think this change (# 72) needs to be tweaked a bit, as Docker does not decompress tar files with ADD when referencing a remote URL (cf. #2369)

So, instead, this PR adds curl and pipes it directly to tar, which will keep the archive file off the image. I also switched from the jdk:full image to jre:slim, which should knock off 80 mb or so.

[manuel-uberti]

Thanks for this.

[lbradstreet]

Thanks to you both for reminding me about this. Merged.