Align summary values in text email template

Aligning these values in the text email template will make it a little
easier to scan and a little more aesthetically pleasing.

Before example:

```
Deployer: John Doe
Application: Application
Branch: master
Environment: test
Time: 01/09/2014 at 03:44 PM PDT
```

After example:

```
Deployer:     John Doe
Application:  Application
Branch:       master
Environment:  test
Time:         01/09/2014 at 03:44 PM PDT
```