Convert rantfile into rakefile for trema-edge build

[nickkaranatsios]

Most of the ground work is done. Waiting for a rake::builder gem release to confirm compiler errors abort the build as expected.

[yasuhito]

👍

[yasuhito]

"Avoid linking every time you run the rakefile even if the executable hasn't changed" issue on rake-builder
joeyates/rake-builder#21

[nickkaranatsios]

Fix the rakefile so it compiles the cmockery to enable first time compiling smoothly.
2ba5aa7

[yasuhito]

👍

[nickkaranatsios]

I got around the above problem by using the Rake::Task['name'].invoke method but the rake::builder has a target_ prerequisites attribute that can be set but it didn't work. When I get around it I'll check it once again and maybe log another issue to the rake::builder author.