Request package update & rate limit system expansion (#413)

* Initial rework of rework of requester - WIP

* Implementing and checking rate limits - WIP

* implemented coinbene rate limiting shenanigans

* add in remaining WIP

* fixy

* use authenticated rate limit

* drop ceiling as this can be done with a counter later

* add functionality to struct

* purge config options for rate limiting so as to keep things minimal

* prepare futures and swap rate limiting for implementation

* Address linter issues

* Addressed nits, fixed race

* fix linter issue

* remove global var as this was only setting when newrequester was called

* moved rate limit functionality into its own file

* Update Bitfinex with correct rate limit and test endpoints (WIP)

* finish off bitfinex adjustments

* fixes

* fix linter issues

* slowed rate for coinbasepro

* drop rate limit for huobi as the doc times have intermittent 429 issues.

* Set MACOSX_DEPLOYMENT_TARGET to remove linking warning

* Addr Thrasher nits

* Addr glorious nits

* unexport do request function

* fixed nitorinos

* Fixed something I missed

* move disabled rate limiter into loadexchange and use interface functionality

* Add temp quick fix

exchanges/interfaces.go

@@ -72,4 +72,6 @@ type IBotExchange interface {
 	GetBase() *Base
 	SupportsAsset(assetType asset.Item) bool
 	GetHistoricCandles(pair currency.Pair, rangesize, granularity int64) ([]Candle, error)
+	DisableRateLimiter() error
+	EnableRateLimiter() error
 }