add pbGetPost function and modify .createPush for this

[mrchypark]

add function to get post using pushbullet api https://docs.pushbullet.com/#list-pushes.

only add param limit first.

[eddelbuettel]

Looks pretty straightforward and clean adding the new param at end to .createPush -- thanks!

[eddelbuettel]

Can you think of a possible test? For now a few lines in simpleTests.R would do.

[mrchypark]

Can you explain about simpleTests.R now? If it can check post count, will be great.

I set test post count == 0 first, and test again end of test and check post count > 0.
Is it right beginning of test, post count is 0?

or maybe all case of test post count > 0 would be fine.

[eddelbuettel]

Yes count changing from zero to greater than zero after we do one of the pushes should do.

[eddelbuettel]

Made a minimal change to "plural" in the function name as multiple posts may get returned.