simplify locales

Author:    Claudio Canepa <ccanepacc@gmail.com>
updatet .travis.yml to support two locales - eliminated abreviations in imports
compat 2.x in locale linux codepath
test_rss_feeds initializes LocaleBorg in setUp
LocaleBorg services as instance methods to ensure initialization
reshaping paranoid damage control forcalendar in windows
allow configure which locales in testing with environmet variables NIKOLA_LOCALE_DEFAULT and NIKOLA_LOCALE_OTHER
update changelog
addresed kw review
fixed remaining _linux -> _posix
Merge pull request #818 from ccanepa/better-locale

simplify locales