fix(docs): A couple spelling mistakes on chart_tests.md

GitHub got more fussy about markdown

Fix typo: Update using_helm.md

bump download links to 2.4.2

they are currently set to 2.4.1.

Missed these on my PR last night

fix(docs): Updated non-working example in 'Using Helm' documentation

fix(docs): Fixing mariadb spelling mistake

Closes #2527

fix(plugins): exists --> exist

fix(tiller): Adds missing import back

PR #2513 was behind master when merged. Other commits were
added that required the use of the log package. This re-adds
that package.

feat(tiller): Adds more logging

This builds on previous work and adds more logging to follow
the full process of installing, updating, deleting, and rolling back.
This also standardizes capitalization of logs and small formatting
fixes

Add --force to upgrade and rollback to delete/create when conflicts

Check existence of $HELM_HOME/plugins before installing plugin

Adds alias for dependencies

fix(docs): Remove "no nested globals allowed"

Add check to stop helm 'waiting' for external services to become ready

Remove incorrect statements in charts.md about nested globals not being allowed.

Fixes https://github.com/kubernetes/helm/issues/2488

Errors out if install/upgrade fails to load-requirements

helm reset --force would clean a failed tiller deployment

- [ ] Fixes https://github.com/kubernetes/helm/issues/2441

ref(docs): remove unnecessary docs and clean up doc generator

ref(tiller): refactor tests into logical files

TestInstallRelease_WithChartAndDependencyNotes  -> tiller/release_install_test.go
TestInstallRelease_WrongTillerVersion -> tiller/release_install_test.go
TestInstallRelease_WithNotesRendered -> tiller/release_install_test.go
TestInstallRelease_TillerVersion -> tiller/release_install_test.go
TestInstallRelease_FailedHooks -> tiller/release_install_test.go
TestInstallRelease_ReuseName -> tiller/release_install_test.go
TestInstallRelease_WithNotes -> tiller/release_install_test.go
TestInstallRelease_NoHooks -> tiller/release_install_test.go
TestInstallRelease_DryRun -> tiller/release_install_test.go
TestInstallRelease -> tiller/release_install_test.go