Simplified how http read timeouts are handled.

Deprecated #default_read_timeout on AWS::Core::Http::Request.
SWF is the only service that (currently) needs to modify
the read timeout (for long polling operations).  Now using
the #read_timeout attribute exclusively to deal with this.
Removed customizations from AWS::SQS::Request.

This is the next step in removing service specific
hooks from the http request classes.
Removed customizations from AWS::Glacier::Request.
Resolved an eager_autoload! bug.

Fixes #237