Auto merge of #2562 - smaximov:doc-add-env-vars, r=alexcrichton
authorbors <bors@rust-lang.org>
Tue, 12 Apr 2016 15:14:33 +0000 (08:14 -0700)
committerbors <bors@rust-lang.org>
Tue, 12 Apr 2016 15:14:33 +0000 (08:14 -0700)
Document env vars introduced in PR #2523 to the docs

Document environment variables introduced in #2523 (`CARGO_PKG_NAME`, `CARGO_PKG_DESCRIPTION`, `CARGO_PKG_HOMEPAGE`).


Trivial merge