Doc changes

All cosmetic changes to make Walker look more awesome.
- Moved documentation links near to top of README
- Added console screenshot
- Added/updated to godoc-style package comments to our subpackages
- Some wording changes in the console (also for the sake of the screenshot)
- Uncommented keys `walker.yaml` -- I liked them commented because it made it super clear that you don't need a walker.yaml at all to run walker, but it also made it hard to read the file. Decided just to uncomment the keys so it looks nice and clear
Not advocating it's use, but this (untested/uncompiled) code looks pretty close to what we would need.

package main

import "fmt"
import "strings"

const (
	_           = iota // ignore first value by assigning to blank identifier
	KB int64  = 1 << (10 * iota)
	MB
	GB
	TB
	PB
	EB
	ZB
	YB
)

// parse strings like 1kb, 45MB, etc.
func parseSizedNumber(input string) int {
	var number int
	var letters string
	//XXX: might need to special case this if you want to accept 100 to mean 100B
	n, err := fmt.Sscanf(input, "%d%s", &number, &letters)
	if err != nil {
		panic(err)
	}
	letters = strings.ToUpper(letters)
	switch letters {
	case "B":
		// do nothing
	case "KB":
		number *= KB
	case "MB":
		number *= MB
	case "GB":
		number *= GB
	case "TB":
		number *= TB
	case "PB":
		number *= PB
	case "EB":
		number *= EB
	case "ZB":
		number *= ZB
	case "YB":
		number *= YB
	default:
		panic("With some error")
	}

	return number
}