Fix attachments with = in filename
* Limit split to first match of = to prevent creating a list of more than two parts
* Add example email with attachment name and test for issue
* Adds functionality to extract charset info from eml files
* Adds missed file-like object handling in detect_file_encoding
* Adds functionality to replace the MIME encodings for eml files with one of the
common encodings if a unicode error occurs
* Organize the eml example files in the example-docs/eml directory
