Swap semacode for dmtx

[ksylvest]

Context

#119

semacode has a lot of issues installing via the native extensions with newer build tools and isn't maintained. dmtx is a strictly ruby Data Matrix generator that might be a suitable replacement.

Testing

The format of the data matrix changed in the testing. To verify that the change worked generated a PNG / SVG and confirmed both still scan with an iOS barcode scanner. I'm a bit unclear on if further verification is required

require 'bundler/setup'
require 'barby'

require 'barby/outputter/cairo_outputter' 
require 'barby/outputter/html_outputter'
require 'barby/barcode/data_matrix'

barcode = Barby::DataMatrix.new('humbaba')
File.write('humbaba.svg', barcode.to_svg)
File.write('humbaba.png', barcode.to_png)

PNG

SVG