Support parsing fairly complex pipelines with groovy surrounding them

Fix some minor glitches in the CLI

Make the CLI give better error messages

e.g.

```
❯ ./target/debug/jdp check data/invalid/no-steps-in-stage/Jenkinsfile

data/invalid/no-steps-in-stage/Jenkinsfile
------------------------------------------
1:     agent any
2:     stages {
3:         stage('Build') {
4:         }
  ---------^

Failed to parse: missing required syntax
```

A lot more advanced grammar parsing, including when { } directives.

This release also pushes to crates.io for an easy `cargo install jdp`

This is a simple checkpoint release that parses some less complex Jen…

…kinsfiles