Simplify pricing plan

[Marak]

Forcing a user to choose a pricing plan up-front makes little sense for a service that is essentially metered.

For now, we should remove all pricing tiers and only offer one paid plan. From this paid plan, we should offer piece meal upgrades for services such as a custom SSL / custom domains / etc.

In regards to limits on hook executions / database documents / etc. We should up all the default limits ( for now ) and monitor usage to determine if any users are getting towards the tops of those limits. From here we can figure out how much to charge for additional usage.

It's important to note that the usage restrictions on the API are actually more intended to prevent accidental abuse ( such as putting an infinite loop on service execution or database insertion ), then for limiting usage of the platform.

Related #107 #124