Add travis ci

[gnzlbg]

@japaric I've added travis-ci support for this. Maybe you could enable travis for this repo and activate it to run periodically, since at least some parts of the puzzle (which I've left commented out) are broken.

In particular, AddressSanitizer builds in --release mode fail to compile, but I couldn't find a report about this anywhere. Is this a regression?

The MemorySanitizer failing to work with cargo test is reported here: rust-lang/rust#39610 so that's not a regression.

From the docs it looks like the LeakSanitizer should work, but I have not managed to make it work. The examples don't fail anymore. Is this a regression? It compiles in my project, but then fails at run-time with a weird error message: https://travis-ci.org/gnzlbg/slice_deque/jobs/336126105#L473

==4161==LeakSanitizer has encountered a fatal error.
==4161==HINT: For debugging, try setting environment variable LSAN_OPTIONS=verbosity=1:log_threads=1
==4161==HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)

The ThreadSanitizer is the only sanitizer that seems to work fine.

EDIT: I had only one passing test for the ThreadSanitizer so obviously the data-race false positive reported in rust-lang/rust#39608 did not surface. Now it surfaces just fine, I've added a test to check that setting RUST_TEST_THREADS=1 works around this issue.

[gnzlbg]

So from: travis-ci/travis-ci#9033 it seems that LeakSanitizer doesn't work on travis at all (hence the fatal errors) and that is travis-ci fault.

So I've disabled the leak sanitizer tests, still, all leak sanitizer tests are broken on my machine.

[gnzlbg]

This is basically the report: https://travis-ci.org/gnzlbg/rust-san

The build is green.