DESCRIPTION: Title should be in title case

The `Title` field in the [DESCRIPTION](https://github.com/BecksLab/pfwim/blob/922e2cd0631dc5cc3233075e54d68af291c38b80/DESCRIPTION) file should be in title case to avoid package build NOTE:

```
The Title field should be in title case. Current version is:
  ‘Food Web Construction for paleo communities’
In title case that is:
  ‘Food Web Construction for Paleo Communities
```