Basic Cargo support
Merge pull request #47 from ozkriff/master

Cargo support
build.sh: Only run configure, if necessary

It seems that running configure (and thereby regenerating the Makefile)
makes Cargo think the project needs to be re-built. Since build.sh
always ran configure, Cargo would always rebuild the project, never
recognizing it as fresh.

This commit modifies build.sh to only run configure, if no Makefile
exists, which solves the problem.
Configure Git to ignore Cargo's target directory