Added rust-empty.mk

To build with rust-empty, run the command:

`make gen-lib && make -f rust-empty.mk`
Updated Deps
Added documentation about Rust-Empty to README
Merge pull request #83 from bvssvni/master

Added rust-empty
Makefile: pull deps before building
Merge pull request #85 from cmr/master

Makefile: pull deps before building