Add try_set_state method for OutputPin

[eldruin]

This is an implementation of #200 to gather some opinions and so we can either accept it or close the issue.
This was earlier discussed at #44.

I added a conversion from bool following the usual convention as well as an ops::Not implementation as suggested in #200, which seemed appropriate.

I also added a default implementation for the try_set_state method. This bears the question whether a default implementation for try_set_high() / try_set_low() by using try_set_state() would be useful, so that potential implementors can choose to implement less methods.

It should be noted that adding a default implementation for all 3 methods has the somewhat amusing property of generating an endless loop if none is overwritten.

Closes #200

[eldruin]

Seems like rust-highfive has not run here
r? @therealprof

[ryankurte]

idea seems good to me!

It should be noted that adding a default implementation for all 3 methods has the somewhat amusing property of generating an endless loop if none is overwritten.

definitely think we only want to default impl one of these (probably try_set_state) because this situation is, v cursed to come across.

[eldruin]

@therealprof What do you think about this?

[therealprof]

LGTM

[eldruin]

Seems we all agree.

bors r=therealprof

[bors]

Build succeeded:

• ci-linux (1.35.0, x86_64-unknown-linux-gnu)
• ci-linux (stable, thumbv6m-none-eabi)
• ci-linux (stable, thumbv7m-none-eabi)
• ci-linux (stable, x86_64-unknown-linux-gnu)