0.48.0: Introduce currency converter mechanism (#724)

This CL introduces a mechanism to fetch currencies rates periodically from a remote source.
Those rates are stored in `CurrencyConverter` struct which can be injected in PBS to get rates.

This doesn't introduce any changes in PBS workflow just yet.

It also address issues described in #722 regarding httptestClient overload in tests generating
errors while running `validate.sh` script.

Issue: #280

0.47.1: Fixes deprecated bidders not being removed from request.imp.ext (#726)

* Fixes deprecated bidders not being removed from request.imp.ext

* Removed a stray Printf

* Removed unused import

0.47.0

Removes the buggy currency code (#723)

0.46.0: Initial RhythmOne Prebid Server Adapter (#704)

* Initial RhythmOne Prebid Server Adapter

* Updated UserSync URL

* Fixed gofmt issue

* Code review comments updated, UserSync URL updated

* Updated code based on review comments - Removed unused client parameter in NewRhythmoneBidder method

* Incorporated review comments

* Updated adapter with resolved conflict

0.45.0: Default ttl per media type (#697)

* Adds support for default cache TTLs per Imp media types

* Fixes bugs in tests

* Fixes issues identified in PR review:

* Refactors existing test into a JSON driven format, and adds new tests

0.44.0: Support sending a TTL parameter to prebid cache (#684)

* Adds support to send TTL to cache

* adds a test

* Fixes a couple of review issues

* Uses existing JSON compare

0.43.4

Fixes a test to match the IP cleaning patch (#689)

0.43.3

Fixed the Domain and Page for AMP requests. (#685)

0.43.2

Makes the masked IP a   IP (#682)

0.43.1

Fixes panic with cleaning blank IPs (#676)