Cleanup of Vagrant install guide

[rajagp]

During workshop, quite a few folks were a bit confused with the vagrant install guide
Specifically the statement

• "If you're not running this on the day of Couchbase Connect, or don't want to take advantage of the pre-supplied files and instead let them get downloaded automatically, skip the rest of this section and move on to Spin Up & Install: Couchbase Server"

  • Remove references to Couchbase Connect
  • Clarify what "pre-supplied" files refer to. There will be no "pre-supplied" or USB sticks going forward. Please upload relevant stuff to GitHub and update the instructions accordingly
  • What is meant by "downloaded automatically". Specifically what do you mean by "automatically"

• "If you're running through this workshop on the day at Couchbase Connect Silicon Valley, "

  • Remove all references to Couchbase Connect in the guide and make the instructions generic

• Clarify the use of "connect_sv.box" . Basically , update the content so that we assume that users will download installers from GitHub

CC @JFlath