slugbuilder: Bump buildpacks
slugbuilder: Bump buildpacks

https://github.com/cloudfoundry/staticfile-buildpack/compare/e1a25f29...8f0d070e
https://github.com/heroku/heroku-buildpack-ruby/compare/e9e442eb...52b7238c
https://github.com/heroku/heroku-buildpack-nodejs/compare/a8cf29ac...8010e251
https://github.com/heroku/heroku-buildpack-clojure/compare/d32e0ed0...e2ee58b4
https://github.com/heroku/heroku-buildpack-python/compare/c98615cd...92b4f5e8
https://github.com/heroku/heroku-buildpack-java/compare/366800fc...ecbd6949
https://github.com/heroku/heroku-buildpack-scala/compare/0ec0cfed...01ef3f24
https://github.com/heroku/heroku-buildpack-php/compare/f9896322...2c8d01ff
https://github.com/heroku/heroku-buildpack-go/compare/7d75a003...70eee647

Closes #2780

Signed-off-by: Jonathan Rudenberg <3692bfa45759a67d83aedf0045f6cb635a966abf@titanous.com>
flynn/flynn,flynn/flynn,philiplb/flynn,lmars/flynn,flynn/flynn,lmars/flynn,flynn/flynn,philiplb/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn,lmars/flynn,philiplb/flynn,lmars/flynn,lmars/flynn