fix logrus updated package name (lowercase)

See https://github.com/sirupsen/logrus/issues/570#issuecomment-313933276

.travis.yml

@@ -55,7 +55,7 @@ install:
   - go get -u github.com/lib/pq
   - go get -u github.com/hashicorp/go-version
   - go get -u github.com/satori/go.uuid
-  - go get -u github.com/Sirupsen/logrus
+  - go get -u github.com/sirupsen/logrus
   - go get -u github.com/pkg/errors
 
 script:

doc.go

@@ -233,7 +233,7 @@ Logging
 
 pgx defines a simple logger interface. Connections optionally accept a logger
 that satisfies this interface. Set LogLevel to control logging verbosity.
-Adapters for github.com/inconshreveable/log15, github.com/Sirupsen/logrus, and
+Adapters for github.com/inconshreveable/log15, github.com/sirupsen/logrus, and
 the testing log are provided in the log directory.
 */
 package pgx

log/logrusadapter/adapter.go

@@ -1,10 +1,10 @@
-// Package logrusadapter provides a logger that writes to a github.com/Sirupsen/logrus.Logger
+// Package logrusadapter provides a logger that writes to a github.com/sirupsen/logrus.Logger
 // log.
 package logrusadapter
 
 import (
-	"github.com/Sirupsen/logrus"
 	"github.com/jackc/pgx"
+	"github.com/sirupsen/logrus"
 )
 
 type Logger struct {