Cleanup and small fixes

[williamthome]

This PR:

• Removes trailing whitespaces and extra ending new lines;
• Removes non-used headers;
• Try to fix the ex_doc warning:

===> warning: the VM is running with native name encoding of latin1 which may cause Elixir to malfunction as it expects utf8. Please ensure your locale is set to UTF-8 (which can be verified by running "locale" in your shell) or set the ELIXIR_ERL_OPTIONS="+fnu" environment variable

• Fix float warnings

Warning: matching on the float 0.0 will no longer also match -0.0 in OTP 27. If you specifically intend to match 0.0 alone, write +0.0 instead.

• Use -type and -spec attributes instead of defining them in docs.

[mworrell]

Merged!

And big thanks!

[mworrell]

Released 2.9.0 and upgraded zotonic master.

[williamthome]

Nice! Thank you!