fix nplurals=1

[OleksiiKukuruza]

fix for languages with nplurals=1

correct formatting:
msgid "{{count}} apple"
msgid_plural "{{count}} apples"
msgstr[0] "{{count}}つのリンゴ"

current behavior:

msgid "{{count}} apple"
msgstr "{{count}} apples"

[coveralls]

Coverage increased (+0.06%) to 96.624% when pulling 7f4d6c4 on OleksiiKukuruza:master into 6ef5a20 on i18next:master.

[perrin4869]

Thank you for the PR! Could you add regression tests?

[perrin4869]

Thank you!!! Some day I'd like to make this code more functional ><;;
Will publish shortly!