Support value argument style for utility function

`t(path, a, b, c)` and `t(path, [a, b, c])` are equal.

Related to #19
Fixes #20
Merge pull request #21 from dockyard/bc-support-value-argument-style

Support value argument style for utility function
Moving helper tests to util tests

The helper tests were there to support when utility function wasn't
working. They are better purposed for unit tests of the utility function
itself.
Merge pull request #22 from dockyard/bc-move-tests

Moving helper tests to util tests
Show how values for interpolation are passed to t