Release nightly/snapshot builds of all jackson modules

[Spikhalskiy]

Hi,

It's possible to find SNASHOT versions of jackson-databing in sonatype snapshot repo, but it's a but hard for some other components, even for a core.
This is how repo for databind looks like: https://oss.sonatype.org/content/repositories/snapshots/com/fasterxml/jackson/core/jackson-databind/
And this is how repo for datatype components looks like:
https://oss.sonatype.org/content/repositories/snapshots/com/fasterxml/jackson/dataformat/jackson-dataformat-csv/
So, it's empty or pretty outdates. Would be great to fix publishing of all modules.

[cowtowncoder]

I suspect this is due to travis set up from .travis.yml, and if so PRs would be welcome. I did not set up travis build up, but have tried to improve those over time,