This refreshes docs, as discussed in #719, and adds a few new sections
to the docs.

Closes #719

This removes the requirement that a fetch or install command must
explicitly state the version number to install. Instead, this goes to
the strategy used by OS package managers: Install the latest until told
to do otherwise.

Closes #1198

Closes #1271

The old form is marked deprecated.

Relates to #1196

Fix typo in using_helm.md that refers to "glide install".  The
reference should be to "helm install".