* reformatted the entire document to look pretty in both standard text and
Markdown
* incorporated [my OS X 10.8 build instructions with Homebrew as the package
manager](http://bitcoin.stackexchange.com/questions/3672/trouble-compiling-bitcoind-on-osx-with-homebrew/5253#5253)
* incorporated @gavinandresen's MacPorts and release build instructions based on
an earlier revision of this commit
* added makefile patch necessary for Homebrew compilation to `contrib`
* updated references to files which have since been moved
* added reference to licensing
* added brief summary in case a non-technical user happens upon repo first
* miscellaneous Markdown-isms to make the doc more attractive
* remove unused symlink README -> README.md
I double-checked the makefiles and whatnot to ensure that the README symlink is
not being referenced. It is not. Rather, `doc/README` and
`doc/README_windows.txt` are copied for distribution.
Colin Dean