Correctly handle RELX_OUTPUT_DIR

Change cowboy URL and version to 1.0.0

Fix package fetching

Two issues got fixed:
* The variable name for the package file got changed to PKG_FILE2
  to avoid conflicts with the PKG_FILE from previous erlang.mk versions.
* The way repositories are fetched changed to fix an issue preventing
  fetching the package file *and* the repositories on the same invokation.

Merge branch 'master' of git://github.com/kiela/erlang.mk

Add CT_OPTS