Fix URI encode process

For GET requests, the query params must be correctly encoded and the
urlencoded_data method is not handling utf8 strings.
Change Http::Tiny -> HTTP::Tiny in dist.ini.
self->_persistent_headers was sometimes undef and there was no lazy bit.
Fix for github issue #19 and
https://rt.cpan.org/Public/Bug/Display.html?id=81803
Merge branch 'urlencode' of https://github.com/wreis/Role-REST-Client
Changes
Make sure httpheaders are updated with persistent headers no matter
which order they are initialized in.