Closes#610
Did a QA pass after reports of some issues with the vault setup.
Identified an issue where my local testing was done with 0.20.0,
resulting in some errors on 0.21.0 due to dropping --mlock.
Also did a few other general tune ups as I ran end-to-ends again using
Vault + Systemd instead of vault in dev mode.
Staging views in #minio-docs channel
This commit also generally cleans up the Installation docs and uses /includes/<platform>/steps-*.rst as a pattern for storing platform-specific tutorials within a single root URL.
Finally, due to API rate limits, this commit adds some Makefile magic to allow skipping of sync'ing dependencies. Pass `make BUILD_DEPENDENCIES=FALSE <platform>` to skip building any deps and use what is already in the branch.
