saner assertions for multiline output
simplify iterating through arglist
un-indent shebang for test executables
better emulate `ruby -S` behavior in testing

Per https://github.com/ruby/ruby/blob/7d3db3c/ruby.c#L1383-1391
add tests for rehash, whence, which
undo `assert_output_lines` in tests

It was a dumb idea and it wasn't even implemented perfectly.
add tests for version commands
add tests for `help` and `rbenv --version`
Merge branch 'test-coverage' for MAXIMUM COVERAGE
improve `versions` tests by cd'ing into a clean slate
restore original IFS for hooks
test that IFS in hooks is correct

closes #379
merge upstream
remove irrelevent rbenv tests from test suite
fix expected help output in tests
Merge commit '6ca591a' into develop

Conflicts:
	libexec/erlenv-rehash
	libexec/rbenv-exec
	libexec/rbenv-which
Merge commit '060f141' into develop

Conflicts:
	test/rehash.bats