Update SendGrid documentation to include sendgrid-java library
migration proc update
Add an NFS troubleshooting section
Merge pull request #193 from sendgrid/master

Update SendGrid documentation to include sendgrid-java library
Added details of SendGrid free service.
changing file ext and image tags
updating image tags and file exts
Merge pull request #197 from drnic/nfs_debugging
Wording tweak
Replace `restart` with `restart`

This commit also emphasizes the recommended approach will be to restart
all CC's

[closes cf-docs#197]
renaming and updating image
Style updates