unit tests: helpers.lua: hack to avoid empty popen() result
unit tests: avoid global scope; add missing cimports

temporarily comment out call to vim_deltempdir() to avoid segfault
unit tests: initialize everything
Merge pull request #1144 from justinmk/fixtests

fix unittest issues with busted 2.x
Update busted to 2.0.rc3.

Default to verbose output to show more information in case of errors.
Fix #1031.