243 inception

[skx]

Once complete this pull-request will close #243, by moving our interpreter to the top-level and regarding it as an important program instead of just an example which got special support.

Mostly this should be simple:

• Move the file
• Update the top-level Makefile to compile it.
• Update test/Makefile to compile/use it in the new location.
• Update examples/Makefile to compile/use it in the new location.
• Update the README.md to document it
  • Might was well breakout the garbage collection section too.
  • And simplify the README.md file while we're at it.
• Sanity-check all documentation.
• Sanity-check inception itself.
• Inception should launch the REPL, if no args are specified.