Docs: Updated READMEs

I cleaned up the main readme, as well as 00a and 00b. Mostly just adding
information and converting them to markdown so they are easier to read
on github.
tools: Fix compiling issues on Mac
Make: Check if tinyos-tools is new enough

The new tinyos make system requires tinyos-tools version 1.6.0 or
greater. The major difference is the new `tos-sub-tosdir` script that
replaces %T with the correct paths. This patch adds a check for that
script and prints an error if the tools need to be rebuilt.