Fix to make library to work in local subnet.

Redmine issue: #540
Putting back original commit change

https://github.com/jcw/ethercard/commit/fb99d3f8c1a189e5d3ff824634bb7385d10c62e9
Add documentation on class BufferFiller
Fix to make library to work in local subnet.

Redmine issue: #540
Putting back original commit change

https://github.com/jcw/ethercard/commit/fb99d3f8c1a189e5d3ff824634bb7385d10c62e9
Merge remote-tracking branch 'origin/master'
Merge pull request #128 from Greblys/master

Fix to make library to work in local subnet.