Adjust gists to not require hard coding

Any email template currently requires a subject in content map:
(api/googleservice.py)
```python
subject_map = {
    'welcome': 'Thanks for filling out our interest form!',
    'acceptance': 'Welcome to Purdue Electric Racing!',
}

content_map = {
    'welcome': 'welcome.html',
    'acceptance': 'acceptance.html',
}
```

Both of these can be done in the gist itself.