These disappeared from the RISC-V website, so we'll use local versions
now.

* Remove references to initramfs

* Discuss methods of obtaining Linux/RISC-V without having to compile the kernel from scratch.

* Update README.md

device-tree-compiler was listed in the required packages twice.

zlib1g-dev is listed in the quick start section, but not in this location.  If you skip the quick start and only install the packages listed in the "Obtaining and Compiling the Sources" section, ./build.sh will fail due to missing zlib (on systems that don't have this library already -- my fresh Ubuntu 16.04 vmware install did not).

Without this option, busybox will try to find /etc/rcS instead of inittab, and the initramfs of this README won't work.

Note, this might not be a complete or even minimal list, but
it's a start and might take out a tiny bit of frustration.

README fixes: Replaced the block device instructions (which are no longer working) with initramfs, and updated "Help, it doesn't work!" section

I changed links to use https instead of http when possible.

[README] Add wget to the Mac OS X homebrew install instructions, since this tool is not installed by default.

add build-basic as build-spike-only and update readme

There are many broken links in the third part of the manual,
which are fixed now.
Right before the "Help!" section, there was a command:
	spike +disk=root.bin vmlinux
which should be
	spike +disk=root.bin bbl vmlinux
and now it is fixed as well.

Finally about style, I think that the references provided originally
in subsection 10 of Linux manual are actually of a whole-project
scope, and thus can be move up a level.

Suggested by #12.

The last commit was suppose to be applied to the new_privileged_isa branch regarding bbl.