Embed PipelineResources in PipelineRun and TaskRun

[ncskier]

Changes

Fixes #240

This PR updates our PipelineRuns and TaskRuns to use an embedded PipelineResourceSpec. So, we will no longer encounter race conditions between the PipelineResources and PipelineRun/TaskRun.

I updated the Gopkg.toml file to use revision 8871979dfc08fb65ae544c6ad2de83f8bab617b0 of tektoncd/pipeline, so we can ensure tektoncd/pipeline#1324 will be available.

Some additional changes had to be made to update to this newer version of Tekton Pipelines. The most notable change is with parameters, where we now must account for the ArrayOrString struct.

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[ncskier]

/uncc @jessm12
/uncc @CarolynMabbott
/cc @a-roberts
/cc @dibbles

[ncskier]

/hold
I talked with @a-roberts and @mnuttall, and we're going to wait on this change until we know we can use this change & Tekton Pipelines version > v0.7.0 in the next kabanero release. Some more info in this comment.

[mnuttall]

Hi @ncskier post-Triggers, we need updated samples for Tekton 0.8+ with the right TriggerTemplates. I think that needs a separate work item so I'll close this.