`helm uninstall/update/install` workflow is wonky

[bacongobbler]

So, given the following use case, say I'm on an older version of a chart that is installed (v0.1.0):

$ helm install postgres

Then, when I want to upgrade to the next version (v0.2.0), I tried the following:

$ helm uninstall postgres
$ helm update
$ helm install postgres

Instead, what I got was v0.1.0. The reason is because the workspace still holds the older postgres version. Since the chart was found in the workspace, it was automatically installed without fetching from the cache. What I expected was for the v0.2.0 chart to be installed, as typically this is the same workflow I use on Homebrew to upgrade old "brews". I've never use brew upgrade as this is the workflow I've been comfortable with when using other package managers like apt, yum, etc.

This is related to #292 but is also a different way to "upgrade" a chart, so perhaps we should either fix this or document it as "working as intended".