Fix getters for register with only wo fields
ioreg: No need to read from write-only registers
Allow registers to have non-'static lifetime
ioreg: Remove 'static from documentation example
Zinc now depends on shiny
ioreg: Add simple testcases
Merge pull request #145 from bgamari/ioreg-write-only

ioreg: write-only register fixes
Merge pull request #142 from bgamari/master

Nightly fallout
Merge pull request #128 from bgamari/ioreg-test

Add rudimentary tests for ioreg