Changing Go default to 1.2, aliasing 1 => 1.2
Retaining go version 1.0 alias to 1.0.3
Defaulting Go version to latest non-tip (1.2.1)

since I'm in there anyway...
And now bumping to go1.2.2 since it's out :smiley_cat:
Adding support for artifacts

refs: https://github.com/travis-ci/travis-artifacts/issues/28
      https://github.com/meatballhat/artifacts
Ensuring the artifacts binary is in $PATH
Changes per feedback on #242
Validating required artifacts params, overriding controlled params
allow some addons to run in paranoid mode

if sudo isn't required then running in paranoid mode should be fine
also pass into the stage
Silencing stderr from initial artifacts check
Removing initial check for `artifacts` binary
Rearranging some of the artifacts addon's steps and echoed messages
Allowing echo of *some* artifacts env vars
More artifacts UX cleanup per feedback
A few more artifacts addon tweaks based on @joshk conversation :smiley_cat:
Breaking out non-runnable messaging, constantizing some settings for artifacts addon
Raising artifacts max-size to 50MB, handling branch config better

per feedback on #242
Adjusting messaging around current branch being runnable in artifacts
Double-quoting all artifacts env vars

so that the array-ish values that are rolled into ";"-delimited strings
don't result in unexpected executions, mostly...  and also for "safety" (?).