Use title case for the DESCRIPTION 'Title' field

The 'Title' field should be in title case.

From [Writing R Extensions](http://cran.r-project.org/doc/manuals/r-release/R-exts.html)

```
The mandatory ‘Title’ field should give a short description of the package. Some package listings may truncate the title to 65 characters.
It should use title case (that is, use capitals for the principal words), not use any markup, not have any continuation lines, and not end in a period.
```