Split chart utils in a different package. Add Gopkg files and unit tests

[andresmgot]

• Added Gopkg.toml, Gopkg.lock and update vendor dependencies (generated after dep init)
• Move charts specific functions to a package. Added tests for FindChartInRepoIndex
• Added unit tests for the controller method updateRelease

[andresmgot]

You've combined 3 separate changes into one PR, which makes it more difficult to review

Yes, I wanted to make a separate PR for the Gopkg changes but I needed the changes for the controller unit testing. I could also have done a separate PR for the unit testing of the chart-utils pkg but since it include some small changes I wanted to ensure that the e2e functionality is not broken with the controller tests.

In any case, if you still want me to split this in three different PRs just let me know.