Fix warnings in build scripts and examples

[austinglaser]

Fixes #57

The build scripts were missing dyn on the boxed error type; fixing those is a no-brainer.

Additionally, there were warnings about unused Results in the logging apps. I chose to explicitly ignore them (preserving the precise behavior which before had been implicit). But there might be an argument for unwraping them instead, or demonstrating more idiomatic error-handling.

In any case, it may be worth adding some discussion about how error handling is basically being ignored here in favor of communicating other concepts. Apologies if it's already there - I'm still working through the book myself.

Would anyone be interested in a section on idiomatic error handling in embedded rust? Is that a better fit for the embedded book rather than the embedonomicon? I'll admit that I don't really know much about this topic myself yet, but I'm interested to learn, and I'd be happy to strike up a dialogue with some folks who do have ideas there, do some drafting, and get some feedback/editing. If anyone's interested in this I'll open a separate issue to discuss in more depth.

[rust-highfive]

r? @thejpster

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[korken89]

bors r+

[bors[bot]]

Build succeeded

• continuous-integration/travis-ci/push