Use markdown for integration body.

I was able to convert the headers to Markdown using these commands:

```
find ./website/partners/integrations/ -type f -iname "*.hbs" -exec sed -i.bak 's/COMPANY/##### Company/g' "{}" +;

find ./website/partners/integrations/ -type f -iname "*.hbs" -exec sed -i.bak 's/INTEGRATION/##### Integration/g' "{}" +;

find ./website/partners/integrations/ -type f -iname "*.hbs.bak" -delete
```