Release 0.3.1

[ConnorJC3]

Issue #, if available: N/A

Description of changes:

Bump all go dependencies (Fix pkg/client/csi_client.go based on dependency API changes)
Recompile protogen files with latest version of protoc and protoc-gen-go
Bump version in Makefile

$ make test
go test ./... -race
?   	github.com/awslabs/volume-modifier-for-k8s/pkg/client	[no test files]
ok  	github.com/awslabs/volume-modifier-for-k8s/cmd	1.122s
?   	github.com/awslabs/volume-modifier-for-k8s/pkg/rpc	[no test files]
?   	github.com/awslabs/volume-modifier-for-k8s/pkg/util	[no test files]
ok  	github.com/awslabs/volume-modifier-for-k8s/pkg/controller	7.083s
ok  	github.com/awslabs/volume-modifier-for-k8s/pkg/modifier	1.078s

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[torredil]

/lgtm
/approve