Clean up categories

Added links to apps, to the app page in portal
Changed SMTPAPI to SMTP API and added a header to the code block to match other code blocks in docs
Fixed linking issue

missed a / in the URL
updated to mkt-api v2 footer
Merge pull request #634 from DynamicDyno/upgrade-footer-api-call

updated to mkt-api v2 footer
add note to disable sslv3
Merge pull request #582 from mbernier/patch-13

Merged
Merge pull request #637 from sendgrid/develop

Merge from Develop