Update the firware binary to work with latest cc3200-rs

[fabricedesre]

Changes in this PR are:

• Update to current cc3200-rs master
• src/main.rs is now a simple runner, right now sending temperature readings.
• the wlan setup moved to wlan.rs
• config.rs.sample needs to be copied to config.rs with your actual parameters.

[fabricedesre]

ping @dhylands Travis seems to have a hard time with cargo right now...

[fabricedesre]

@dhylands I addressed comments and pinned Rustc to the same version as in cc3200-rs. That fixed the unrelated cargo issue which is https://github.com/rust-lang/cargo/issues/3340

[dhylands]

lgtm