Bump to an NQP with native call improvements.

Both MoarVM support, and JVM improvements.
Convert README to Markdown
Formatting updates for README.md
Merge branch 'nom' of https://github.com/rakudo/rakudo into nom
Factor out some installation information
Simplify build instructions
Move note about different backends and features to top
Make some links more pleasant
Clarify JVM memory limit instructions
Formatting and clarification on `--backends`
Formatto
At least mention a file we *do* keep updated

(as opposed to the poor, neglected docs/compiler_overview.pod)
&pack: Add 'a' directive and be more frugal with 'A' and 'a'
Merge branch 'nom' of github.com:rakudo/rakudo into eleven