(doc) Sync latest CONTRIBUTING.md

This is the latest CONTRIBUTING.md from
https://github.com/puppetlabs/puppet/blob/master/CONTRIBUTING.md

The old version has out of date links.
(doc) Update links for modules

For modules, the JIRA project is MODULES not PUP.
Link to the module contributing guide, instead of core puppet
(doc) Update link to JIRA

Issue tracking has been moved from github to JIRA.
Merge pull request #343 from skurylo/update_docs

Update CONTRIBUTING and README