Fix closing maven central staging repo request to allow skipping closing

[lukaszwawrzyk]

I haven't tested if this is a bug, but it seems like one.
As stated in bintray api documentation here,

By default the staging repository is closed and artifacts are released to Maven Central. You can optionally turn this behaviour off and release the version manually. This is achieved by passing 0 in the 'close' field of the JSON passed to the call.

So it seems that in order to close the repo we need to pass "1" or nothing, and to leave it open, we should pass "0" explicitly. Currently, the code seems to pass "1" if method is called with close = true, and pass null (?) if method is called with close = false. Which would mean it will be closed regardless of what is passed.
I changed the code to be explicit about the close and always send either "1" or "0".

So please correct me if this is wrong. If this is correct, I would like to ask for a possibly quick merge and release. After this I am planning to update sbt-bintray plugin to expose this closing via a setting.
Thanks.

[dwijnand]

hi @lukaszwawrzyk! sorry for making you wait so long for this review, I've been hung up on a long task these days and didn't have a chance to slow down and read what you said.

I agree with your assessment. this is good to go, and I'll merge it now, and release either later today or tomorrow.

btw from my reading of the code if close were ever false it would actually throw at runtime: https://github.com/json4s/json4s/blob/v3.4.2/native/src/main/scala/org/json4s/native/JsonMethods.scala#L38