Localize ascii incompatible countries

[arkid15r]

Add en_US localization for:

• Armenia
• Belarus
• Bulgaria
• Canada
• Cyprus
• Ethiopia
• Georgia
• Greece
• Japan
• Russia
• Serbia

Update po generation files script. Update MANIFEST.in. Update README.rst. Fix packaging.

[coveralls]

Coverage: 100.0%. Remained the same when pulling 996bc62 on arkid15r:localize-ascii-incompatible-countries into d267936 on dr-prodigy:beta.

[PPsyrius]

A bit minor note: I did try switching to having Thai text as default based on this PR, and the issue still persists when using make l10n as you can see below:

holidays/locale/pot/TH.pot:53: warning: The following msgid contains non-ASCII characters.
                                        This will cause problems to translators who use a character encoding
                                        different from yours. Consider using a pure ASCII msgid instead.
                                        พระราชพิธีฉลองสิริราชสมบัติครบ 60 ปี พ.ศ. 2549
holidays/locale/pot/TH.pot:53: invalid multibyte sequence
holidays/locale/pot/TH.pot:53: invalid multibyte sequence
holidays/locale/pot/TH.pot:53: invalid multibyte sequence
holidays/locale/pot/TH.pot:53: invalid multibyte sequence
holidays/locale/pot/TH.pot:53: invalid multibyte sequence
holidays/locale/pot/TH.pot:53: invalid multibyte sequence

With this in mind, I'm considering continuing my approach on #946 instead, but will switch around the test cases to generate our desired result of having th as default and en_US as supported.