yaml parsing error message is not helpful

# Steps to reproduce:
 1. Create a file with invalid yaml
 2. Run `rif <that file>`

# Current output:
```
Error parsing .rif file: yaml: unmarshal errors:
  line 1: cannot unmarshal !!str `cmake_m...` into fileversions.RifYamlFileV0
```

# Desired output
Something more like:
```
Error: <filename> is not valid yaml
```