Buffer rewrite/encoding

[calvinmetcalf]

for use in tandem with calvinmetcalf/parseDBF#10

[calvinmetcalf]

this change brings the size from 60KB to 234KB, almost all of that is for non utf8 encodings

[calvinmetcalf]

actually more like 260k, and 200k is from iconv lite

[calvinmetcalf]

gzipped and minified sizes for various options, in bytes

Option	Size
original	59,172
just utf8	60,363
IE needs a shim for non-utf8	65,676
all encodings	236,209

[calvinmetcalf]

ok if we use the polyfill and require IE users who want other encodings to include a file then we can do it in 65676 bytes, though it's waiting on inexorabletash/text-encoding#70

[calvinmetcalf]

done