Remove duplicate header from iso8601 curl example

The "-H 'Content-type: application/json'" flag was duplicated in the
/scheduler/iso8601 example. The flag only needs to be there once.
Add note about epsilon ISO 8601 Duration formatting
Link to SSL versions of Apache projects
Capitalize "Chronos" and "Mesos"
Bold unbolded methods to match others
Merge pull request #155 from mesosphere/readme-touchups

Readme Touchups