Make a test more resilient against the host system

If the host system had $HOME/.cargo/config which configured a user name/email
then this test would fail because those would be prioritized over $USER.

Closes #514
Update dependencies
auto merge of #655 : ebfe/cargo/deps, r=alexcrichton

At least rust-encoding needs updating to compile with rust master.
auto merge of #631 : alexcrichton/cargo/issue-514, r=brson

If the host system had $HOME/.cargo/config which configured a user name/email
then this test would fail because those would be prioritized over $USER.

Closes #514
Install materials to comply with upstream licenses

This follows #656 by mentioning OpenSSL in the README, as well as install all
license files on installation. A hand-generated LICENSE-THIRD-PARTY is also
included.

Closes #656

This also approaches #657 by mentioning that we have GPL software in the README.
Cargo will hopefully support a more complete "all source" distribution in the
future, but at this time there is not an easy way to generate a complete source
tarball via cargo.