Use correctly sized gravatars when possible

Provides a gravatar_fixup vmethod that accepts a pixel size to set on
gravatar URLs.  It also adjusts them to use HTTPS, replacing the
existing repeated templated code.
Merge pull request #1206 from haarg/gravatar-fixup

Use correctly sized gravatars when possible
Fixes Dist::Zilla search precision test.
Move plussers to right and limit - start of #1184