add instrumentation middleware.  original work by @mislav

https://github.com/pengwynn/faraday_middleware/commit/23d5e614eea4f48dd5
a0eee68eb8b3d5e65b5275
Merge pull request #228 from lostisland/instrumentation

add instrumentation middleware.
match against ActiveSupport anywhere in the error name
ok rbx handles NameError differently
faraday/autoload requires faraday
remove some duplication from faraday.gemspec.  add scripts
releasing pushes to legacy remote
merge instrumentation middleware
disable legacy with env var