Merge pull request #17 from cmr/master

pkgid and make dead code public
New ApproxEq replaced the one in std
Fixed tests that used assert_approx_eq
Merge pull request #21 from kvark/try-approx

Reimplement ApproxEq that has been removed from the standard library
Fix renamed structures:
	VecIterator -> Items
	MutVecIterator -> MutItems
Merge pull request #25 from csherratt/Items

Fix build break
Impl appropriate operators for implementors of Zero and One
Reduce code duplication

We can now have multiple definitions in macros!
Merge pull request #27 from bjz/build-fixes

Build fixes
cargo-lite