First crack at updating the readme (#1106)

* First crack at updating the readme
Goals
Include up front example
Simplify
Get users to things quicker
Move complicated details to wiki.

* headers were not working,
intellij and github don't use same render for .md files

* Fix verb agreement

* Add a fir filter diagram
Compact the fir-filter code a bit

* More compact filter

* Additional README.md updates

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Don't use chisel-lang.org, drop HCL

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

* Fix link to fir image, make it relative

* Proposed readme changes

* Resize picture, restyle doc bullets