Adds support for Firebase Cloud Messaging#129

Merged

mbleigh merged 7 commits intomasterfrom messaging

Oct 18, 2016

+379-4

Commits on Sep 28, 2016

First pass. Work to do.
mbleigh
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Add some more to demo.
mbleigh
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Minor tweaks (#23 )

Matthew Gaunt
authored and
mbleigh
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Commits on Oct 6, 2016

updates
mbleigh
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Commits on Oct 10, 2016

Set this.messaging
mbleigh
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Commits on Oct 16, 2016

Depend on 3.5 for messaging.
mbleigh
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Commits on Oct 18, 2016

Improve docs, add note to demo, pass custom sw to activate
mbleigh
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