[DEV-253] Remove dependancy on github.com/pkg/errors (#113)

Gopkg.lock

@@ -92,12 +92,6 @@
   packages = ["."]
   revision = "f71540b9dfdcfe64dbf2818e9b66423c6aafcacd"
 
-[[projects]]
-  branch = "master"
-  name = "github.com/pkg/errors"
-  packages = ["."]
-  revision = "d58f94251046e7f70ac45aceea6cf6f61415ccca"
-
 [[projects]]
   branch = "master"
   name = "golang.org/x/crypto"
@@ -107,6 +101,6 @@
 [solve-meta]
   analyzer-name = "dep"
   analyzer-version = 1
-  inputs-digest = "8dc0933d88a4dda8879b373d68550cf2211ad8850c9b091d9894c5d21a92a086"
+  inputs-digest = "5976f1edbea819ab26c66eb5e5604c255a72f174b7a47bb218f3b8a6733d0c3a"
   solver-name = "gps-cdcl"
   solver-version = 1

Gopkg.toml

@@ -63,10 +63,6 @@
   branch = "master"
   name = "bou.ke/monkey"
 
-[[constraint]]
-  branch = "master"
-  name = "github.com/pkg/errors"
-
 [prune]
   go-tests = true
   unused-packages = true

blockdag/blockindex_test.go

@@ -1,6 +1,7 @@
 package blockdag
 
 import (
+	"errors"
 	"strings"
 	"testing"
 	"time"
@@ -8,7 +9,6 @@ import (
 	"bou.ke/monkey"
 	"github.com/daglabs/btcd/dagconfig"
 	"github.com/daglabs/btcd/database"
-	"github.com/pkg/errors"
 )
 
 func TestAncestorErrors(t *testing.T) {