Remove colons from NSQ filenames

[davidstoker]

I recently deployed the S3 loader in a new setup with part of it working like this:

Scala stream collector -> NSQ topic -> S3 Loader -> S3

This works as expected with files being sinked to the S3 bucket with names like this:
2018-02-14-03:52:55.281-03:54:21.489-1579626703.lzo

The ETL process was then kicked off using EmrEtlRunner but would immediately fail on the first step with errors like this:

Exception in thread "main" java.lang.IllegalArgumentException: java.net.URISyntaxException: Relative path in absolute URI: 2018-02-14-03:52:55.281-03:54:21.489-1579626703.lzo

It was a cryptic error at first but then was obvious since HDFS treats colons as special characters. The time format defined here (https://github.com/snowplow/snowplow-s3-loader/blob/master/src/main/scala/com.snowplowanalytics.s3/loader/NsqSourceExecutor.scala#L80) is causing the problem. The Kinesis sink uses different file name handling so the problem doesn't exist there.

Would be glad to open a PR since it's a simple fix but wanted to capture as an issue for any others with the problem. I'm currently operating with a fork that has the time format changed to HHmmssSSS instead of HH:mm:ss.SSS

[alexanderdean]

Ouch, good catch @davidstoker ! A PR would be most welcome. We shouldn't be using :s in filenames in any case (we don't with Kinesis)...