Reword error, and add test.
nicer tests
Merge pull request #37 from howbazaar/fix-time-fail

Reword time between error, and add test.
Add nil checker and makefile.
Tests for IsNil.
tweak message output.
Update for the StackTrace method name change.
Merge pull request #38 from howbazaar/add-nil-checker

Add error aware IsNil checker