Fix parsing of `ruby` version for `ArcanistRubyLinter`
Fix parsing of `ruby` version for `ArcanistRubyLinter`

Summary:
This fails to extract the version correctly locally.

```
> ruby --version
ruby 1.8.7 (2014-01-28 patchlevel 376) [x86_64-linux]
```

Test Plan: `arc unit`

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D14525

haskell-infra/arcanist,coursera/arcanist,fivestars/arcanist,coursera/arcanist,haskell-infra/arcanist,aik099/arcanist,coursera/arcanist,folsom-labs/arcanist,jra3/arcanist,Khan/arcanist,uber/arcanist,aik099/arcanist,jra3/arcanist,calblueprint/arcanist,wikimedia/phabricator-arcanist,wikimedia/phabricator-arcanist,zhihu/arcanist,chundongwang/arcanist,Khan/arcanist,phacility/arcanist,wikimedia/phabricator-arcanist,folsom-labs/arcanist,chundongwang/arcanist,calblueprint/arcanist,uber/arcanist,r4nt/arcanist,calblueprint/arcanist,haskell-infra/arcanist,phacility/arcanist,chundongwang/arcanist,memsql/arcanist,aik099/arcanist,chundongwang/arcanist,calblueprint/arcanist,codelabs-ch/arcanist,uber/arcanist,haskell-infra/arcanist,fivestars/arcanist,memsql/arcanist,zhihu/arcanist,codelabs-ch/arcanist,jra3/arcanist,fivestars/arcanist,r4nt/arcanist,memsql/arcanist,codelabs-ch/arcanist,folsom-labs/arcanist,fivestars/arcanist,coursera/arcanist,codelabs-ch/arcanist,phacility/arcanist,zhihu/arcanist,folsom-labs/arcanist,uber/arcanist,aik099/arcanist,r4nt/arcanist,r4nt/arcanist,zhihu/arcanist,phacility/arcanist,codelabs-ch/arcanist,Khan/arcanist,memsql/arcanist,wikimedia/phabricator-arcanist,jra3/arcanist,phacility/arcanist,Khan/arcanist