Catch invalid job names

[jacobtomlinson]

When trying to create a job with the name runningTest I get the following error.

$ krontab -e
panic: CronJob.batch "runningTest" is invalid: [metadata.name: Invalid value: "runningTest": a DNS-1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*'), spec.jobTemplate.spec.template.spec.containers[0].name: Invalid value: "runningTest": a DNS-1123 label must consist of lower case alphanumeric characters or '-', and must start and end with an alphanumeric character (e.g. 'my-name',  or '123-abc', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?')]

goroutine 1 [running]:
github.com/jacobtomlinson/krontab/crontab.KronJob.Create(0xc0000b5c58, 0x7, 0xc0000b5ca0, 0xb, 0xc0000b5e60, 0xc, 0xc0000b5f10, 0xc, 0x0, 0x18)
        /Users/jacob/Projects/pangeo/krontab/crontab/crontab.go:78 +0xf1
github.com/jacobtomlinson/krontab/crontab.EditCrontab()
        /Users/jacob/Projects/pangeo/krontab/crontab/crontab.go:207 +0x5a1
github.com/jacobtomlinson/krontab/cmd.glob..func10(0x2849f20, 0xc00030ee80, 0x0, 0x1)
        /Users/jacob/Projects/pangeo/krontab/cmd/root.go:32 +0x59
github.com/spf13/cobra.(*Command).execute(0x2849f20, 0xc0000c2030, 0x1, 0x1, 0x2849f20, 0xc0000c2030)
        /Users/jacob/go/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:766 +0x2cc
github.com/spf13/cobra.(*Command).ExecuteC(0x2849f20, 0x0, 0x284a640, 0xc000147f58)
        /Users/jacob/go/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:852 +0x2fd
github.com/spf13/cobra.(*Command).Execute(0x2849f20, 0x1007500, 0xc0000a0058)
        /Users/jacob/go/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:800 +0x2b
github.com/jacobtomlinson/krontab/cmd.Execute()
        /Users/jacob/Projects/pangeo/krontab/cmd/root.go:44 +0x2d
main.main()
        /Users/jacob/Projects/pangeo/krontab/main.go:8 +0x20