Document variable PWM frequency

[monkbroc]

Merge when particle-iot/device-os#756 is merged.

[m-mcgowan]

was the change to API node intentional? not to worry, I'll cherry pick the doc commit.

[monkbroc]

No. Since this is a private sub module, git always complains when I
pull/checkout/merge the docs repo. Occasionally I forget to revert the
change to the API node.
On Jan 21, 2016 2:48 AM, "Matthew McGowan" notifications@github.com wrote:

was the change to API node intentional? not to worry, I'll cherry pick the
doc commit.

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Reply to this email directly or view it on GitHub
#262 (comment).

[monkbroc]

This PR has been cherry-picked into master