Move middlewares into handlers package

[adamryman]

In order to configure middlewares using the NewService function in a more straight forward way, the middlewares package has been moved into handlers.

This means that the function WrapEndpoints is now in the same package as NewService, allowing the middlewares to be configured with package level variables rather than cross package variables.

This is not a complete solution, but rather an incremental improvement to the current configuration situation.

There was no real reason that middlewares became its own package, just a decision I made along the line. Both @zaquestion and @hasLeland agree that it makes sense to be part of the handlers package.

To help with the transition, running these commands in the NAME-service directory in addition to rerunning truss should result in a all old middlewares still functioning.

cat middlewares/endpoints.go | \
    sed 's|^package middlewares|package handlers|' > handlers/middlewares.go

# Note that this creates a file `service_middlewares.go` that truss will not create, 
# though this is easier than trying to combine the files together here.

cat middlewares/service.go | \
    sed 's|^package middlewares|package handlers|' > handlers/service_middlewares.go

rm middlewares/endpoints.go
rm middlewares/service.go
rmdir middlewares

Additionally:

• rename package github.com/TuneLab/truss/gengokit/handler to github.com/TuneLab/truss/gengokit/handlers
• add NewEndpoints to package svc/server

[hasLeland]

In general, a very nice little cleanup of code!

[hasLeland]

I love that this logic is collapsed in the new version