bug 1066058; add Support Reason API crashstorage type

*Preamble: This PR is primarily submitted for discussion purposes (I expect more work to be necessary).*

This adds the `SupportReasonAPIStorage` class which is a sub-class of `BotoS3CrashStorage`; functionally speaking, the former is basically a *highly lossy* implementation of the latter.

cc @twobraids 
* No, the bucket name should be just one for Socorro prod forever. E.g. `mozilla-support-reason-prod` and that'll never change. A "persona" prefix is important, a "instance suffix" is also important. 

* But it's really important that each instance (stage, prod, phrawtzy's laptop, peterbe's laptop) are different. You can only PUT into a S3 bucket named the same if you're using the same credentials. Something we might end up doing for stage and prod. A S3 bucket name needs to be unique in the same sense a DNS domain name needs to be unique. 

* No need for radix sub-directories or anything like that. Simply a constant bucket and then the file (aka key) is the UUID. You never have the problem with `ls` in a filesystem directory where if you put too many files in one place, the `ls` command blows up. S3 doesn't work like that. 

* @bsmedberg the reason for S3 over Dynamo is that 1) S3 has the "Lifecycle" feature (similar to HBase) which is uber-easy to set up and apply and 2) because once stored it's as simply to retrieve by simply doing a HTTP GET with the uuid at the end of the URL.