Following suggestion by reviewer @ikedas: Replacing 'get()' by 'mime_attr()' and, therefore, a regular expression by 'eq'.

Including stub to libraries, so Constants.pm is found. Adding Sympa constants because most of them are needed when using
 Sympa libraries. Specifying the sources 'default' directory for 'DEFAULTDIR' constant to allow access to distributed templates.

  - t/Message.t,
  - t/samples/ contains six different messages for testing urlize,
  - t/data/ now contains a test list configuration file.

1- message text was treated as attachment and remained on the server as either "msg.0.bin" or "msg.0.txt" files. Fixed by testing the part type before urlizing it.
2- some special characters in message id led to the attachment to be considered missing by Sympa.

I had to refactor the code a bit to allow urlizing of nested multiparts.

The detail of urlization treatment is as follows:

1- any multipart/mixed message part will be analyzed to look for urlizable parts,
2- any mulitpart/related message part will be be analyzed to look for multiârt/mixed sub parts,
3- within the multipart/mixed parts, any text/* part whose "Content-Disposition" header is not "attachment" and has a correct Content-Type.charset value is kept untouched,
4- any other subpart is kept on the server an replaced by a download link.

Addition to #829

Deprecate filesystem_encoding parameter

Introduced Sympa::Tools::Text::slurp() to slurp text file applying Unicode sanitization and normalization. Note: Though Unicode::Normalize and Unicode::UTF8 are optional now, they would be mandatory in the future.

Scenario fails with negative indices in [header->Field][n] (#831)

Prevent the error on "Modification of non-creatable array value" by using "[header->Field][-1]" in scenarios.

Rearrange .travis.yml

Fixing a bug injected by 83f6907e (6.2.45b.3). (#822)

Fixes issue #820: sympa_msg.pl: Rejection reports were suppressed

Fixes #820: If a "reject" action in a scenario does not have "quiet" modifier, and the incoming message does not have spam flag, rejection notice will be sent back.

Family: Fixing bugs injected by #771 (#815)

Fixing #813

Updating dependency Test::Pod

Demote Sympa::List debug messages when invoking constructor and load method