Update README.md

Fixed minor typo( :repitition should have been :repetition)
New Grammar ANSI X12 002001

856 Ship Notice/Manifest
work in progress - 002001 \ guide file SH586
first draft guide + tweaks to transaction_set_defs
changes to transaction_set_defs
replaced .header w/ .detail
added SH 856 support
added new message to config.rb

SH 856
SH 856 / 002001 support
SH 856

use FortyTen
SH 856
SH 856
SH 856
SH 856 -Work in progress
SH 856
SH 856
856 SH
SH 856
SH 856

Work in progress defining element_defs based on 002001 Data element
dictionary
SH 856

successful parse via edi-pp
following standard guide now