Rename package logrus in lowercase for go mod compatibility

[fabiocicerchia]

While working on a project of mine which is already using logrus as dependency, I've found the following error while installing the test-reporter:

$ go get -v github.com/codeclimate/test-reporter
go: github.com/codeclimate/test-reporter upgrade => v1.0.1
go: finding module for package github.com/pkg/errors
go: finding module for package github.com/spf13/cobra
go: finding module for package github.com/markbates/pop/nulls
go: finding module for package gopkg.in/src-d/go-git.v4/plumbing
go: finding module for package gopkg.in/src-d/go-git.v4/plumbing/object
go: finding module for package github.com/Sirupsen/logrus
go: finding module for package gopkg.in/src-d/go-git.v4
go: finding module for package github.com/gobuffalo/envy
go: finding module for package github.com/fatih/structs
go: found github.com/Sirupsen/logrus in github.com/Sirupsen/logrus v1.7.0
go: found github.com/gobuffalo/envy in github.com/gobuffalo/envy v1.9.0
go: found github.com/pkg/errors in github.com/pkg/errors v0.9.1
go: found github.com/spf13/cobra in github.com/spf13/cobra v1.1.1
go: found github.com/fatih/structs in github.com/fatih/structs v1.1.0
go: found gopkg.in/src-d/go-git.v4 in gopkg.in/src-d/go-git.v4 v4.13.1
go: found github.com/markbates/pop/nulls in github.com/markbates/pop v4.12.2+incompatible
go: github.com/codeclimate/test-reporter imports
        github.com/codeclimate/test-reporter/cmd imports
        github.com/Sirupsen/logrus: github.com/Sirupsen/logrus@v1.7.0: parsing go.mod:
        module declares its path as: github.com/sirupsen/logrus
                but was required as: github.com/Sirupsen/logrus
make: *** [codeclimate] Error 1

from the official logrus documentation:

Seeing weird case-sensitive problems? It's in the past been possible to import Logrus as both upper- and lower-case. Due to the Go package environment, this caused issues in the community and we needed a standard. Some environments experienced problems with the upper-case variant, so the lower-case was decided. Everything using logrus will need to use the lower-case: github.com/sirupsen/logrus. Any package that isn't, should be changed.

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