Set up test code coverage reports

[farcaller]

It seems that rust binaries can provide coverage data via kcov now that -g is fixed (rust-lang/rust#690). The problem is that kcov doesn't run on either OS X or Linux/arm hosts (the latter is similar to SimonKagstrom/kcov#18), but works perfectly well on Linux/x86_64.

One option is to build coverage data on travis and then upload it to s3. it doesn't deal with historic coverage results though, but will provide overall coverage state for master/HEAD.

[farcaller]

Statically compiled kcov for linux/x86_64: http://vfp.in/kcov.gz

[thehydroimpulse]

I've always wanted to have this in Rust. Have you looked at https://coveralls.io/ ? It has support for Ruby, JavaScript (super hacky though), Go and a few others.

[thehydroimpulse]

It can also be triggered upon a new Travis CI build, and keeps the history behind it.

[farcaller]

Thanks for a hint, I've pinged @lemurheavy on adding rust support in coveralls.

[farcaller]

Coverage is being generated now.
PR: #70
Web: http://cov.zinc.rs/platformtree_test

[SimonKagstrom]

kcov should work better with rust since a few commits back (by Kang Seonghoon), and while I very irregularly test ARM support, there was a few fixes to get it working a few months ago (albeit with very limited testing).

And kcov actually supports coveralls.io as well these days, basically just run it with '''--coveralls-id=$TRAVIS_JOB_ID''' from the travis build script.