Add -fPIC to linker options.

Fixes #179.
Update .gitignore and fix Makefile clean target.
Merge pull request #181 from michaelsproul/fpic-linker

Add -fPIC to linker options.
Merge pull request #182 from michaelsproul/cleanup

Update .gitignore and fix Makefile clean target.
Merge branch 'master' into cmake

Conflicts:
	.gitignore