Don't depend on dcrdata/exchanges. (#190)

* Don't depend on dcrdata/exchanges.

dcrdata/exchanges depends on decred/dcrdex, which at time of writing has
over 150 dependencies of its own. All of these extra deps can be avoided
by simply copy/pasting the necessary parts of exchanges.ExchangeRates
into this project (grand total two lines of code).

* build: Update gorilla/handlers and dcrutil deps.

go.mod

@@ -3,59 +3,40 @@ module github.com/decred/dcrwebapi
 go 1.18
 
 require (
-	github.com/decred/dcrd/dcrutil/v4 v4.0.0
-	github.com/decred/dcrdata/exchanges/v3 v3.1.0
+	github.com/decred/dcrd/dcrutil/v4 v4.0.1
 	github.com/decred/dcrdata/v6 v6.0.0
-	github.com/gorilla/handlers v1.5.1
+	github.com/gorilla/handlers v1.5.2
 )
 
 require (
-	decred.org/dcrdex v0.4.3 // indirect
 	decred.org/dcrwallet v1.7.0 // indirect
 	github.com/agl/ed25519 v0.0.0-20170116200512-5312a6153412 // indirect
-	github.com/carterjones/go-cloudflare-scraper v0.1.2 // indirect
-	github.com/carterjones/signalr v0.3.5 // indirect
-	github.com/dchest/siphash v1.2.2 // indirect
-	github.com/decred/base58 v1.0.3 // indirect
+	github.com/dchest/siphash v1.2.3 // indirect
+	github.com/decred/base58 v1.0.5 // indirect
 	github.com/decred/dcrd/blockchain/stake/v3 v3.0.0 // indirect
 	github.com/decred/dcrd/blockchain/standalone/v2 v2.1.0 // indirect
-	github.com/decred/dcrd/certgen v1.1.1 // indirect
-	github.com/decred/dcrd/chaincfg/chainhash v1.0.3 // indirect
-	github.com/decred/dcrd/chaincfg/v3 v3.1.1 // indirect
-	github.com/decred/dcrd/crypto/blake256 v1.0.1-0.20200921185235-6d75c7ec1199 // indirect
-	github.com/decred/dcrd/crypto/ripemd160 v1.0.1 // indirect
+	github.com/decred/dcrd/chaincfg/chainhash v1.0.4 // indirect
+	github.com/decred/dcrd/chaincfg/v3 v3.2.0 // indirect
+	github.com/decred/dcrd/crypto/blake256 v1.0.1 // indirect
+	github.com/decred/dcrd/crypto/ripemd160 v1.0.2 // indirect
 	github.com/decred/dcrd/database/v2 v2.0.2 // indirect
-	github.com/decred/dcrd/dcrec v1.0.1-0.20200921185235-6d75c7ec1199 // indirect
-	github.com/decred/dcrd/dcrec/edwards/v2 v2.0.2 // indirect
+	github.com/decred/dcrd/dcrec v1.0.1 // indirect
+	github.com/decred/dcrd/dcrec/edwards/v2 v2.0.3 // indirect
 	github.com/decred/dcrd/dcrec/secp256k1/v3 v3.0.0 // indirect
-	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.0.1 // indirect
+	github.com/decred/dcrd/dcrec/secp256k1/v4 v4.2.0 // indirect
 	github.com/decred/dcrd/dcrjson/v3 v3.1.0 // indirect
 	github.com/decred/dcrd/dcrutil/v3 v3.0.0 // indirect
-	github.com/decred/dcrd/hdkeychain/v3 v3.1.0 // indirect
 	github.com/decred/dcrd/rpc/jsonrpc/types/v2 v2.3.0 // indirect
 	github.com/decred/dcrd/txscript/v3 v3.0.0 // indirect
-	github.com/decred/dcrd/txscript/v4 v4.0.0 // indirect
-	github.com/decred/dcrd/wire v1.5.0 // indirect
-	github.com/decred/go-socks v1.1.0 // indirect
+	github.com/decred/dcrd/txscript/v4 v4.1.0 // indirect
+	github.com/decred/dcrd/wire v1.6.0 // indirect
 	github.com/decred/slog v1.2.0 // indirect
 	github.com/felixge/httpsnoop v1.0.3 // indirect
-	github.com/go-chi/chi/v5 v5.0.4 // indirect
-	github.com/golang/protobuf v1.4.3 // indirect
 	github.com/golang/snappy v0.0.4 // indirect
-	github.com/gorilla/websocket v1.4.2 // indirect
-	github.com/lib/pq v1.10.3 // indirect
-	github.com/pkg/errors v0.9.1 // indirect
-	github.com/robertkrimen/otto v0.0.0-20180617131154-15f95af6e78d // indirect
+	github.com/klauspost/cpuid/v2 v2.0.9 // indirect
 	github.com/syndtr/goleveldb v1.0.1-0.20210819022825-2ae1ddf74ef7 // indirect
-	go.etcd.io/bbolt v1.3.7-0.20220130032806-d5db64bdbfde // indirect
-	golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97 // indirect
-	golang.org/x/net v0.0.0-20210903162142-ad29c8ab022f // indirect
-	golang.org/x/sys v0.0.0-20210902050250-f475640dd07b // indirect
-	golang.org/x/text v0.3.6 // indirect
-	golang.org/x/time v0.0.0-20210220033141-f8bda1e9f3ba // indirect
-	google.golang.org/genproto v0.0.0-20201022181438-0ff5f38871d5 // indirect
-	google.golang.org/grpc v1.36.1 // indirect
-	google.golang.org/protobuf v1.25.0 // indirect
-	gopkg.in/ini.v1 v1.55.0 // indirect
-	gopkg.in/sourcemap.v1 v1.0.5 // indirect
+	golang.org/x/net v0.20.0 // indirect
+	golang.org/x/sys v0.16.0 // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
+	lukechampine.com/blake3 v1.2.1 // indirect
 )