Previously we just assumed the reader was familiar with the idea of a
graph but didn't explain it.
Since graphs are an implementation detail of Terraform, rather than
essential information needed for new users, this revises the introduction
text to talk only about _dependencies_, which we assume the user is
familiar with as a more practical concept.
Additionally, Paul Hinze did a great talk on how Terraform uses graphs
at HashiConf 2016 which is good additional content for our existing
"Graph Internals" page, which includes a concise explanation of the
basics of graph theory.
* update plugin/provider to make clear this section isn't needed for regular use
* add some links and notes about getting started
* remove the mention of binaries... I 'm not sure it's needed yet
* 'Installing Terraform Providers' section
* sometimes I can't words good
* move the 'installing providers' block
* cleanup of terms
* copy that update to plugins/provider too
Martin Atkins