Don't spit out 1.8 errors for preloaded config

Regression in #105.
Fix error initialization
Fail gracefully when config file is missing or bad

This is better than raising obscure exceptions from the internals.
Rename "variants" to "alternatives"
Merge pull request #108 from iangreenleaf/graceful_failure

Fail gracefully when config file is missing or bad
Removed executables line from gemspec

We don't have any executables to worry about
Version 0.5.0
Merged 0.4.7 and 0.5.0 changelog notes

Turns out 0.4.7 was never actually released!
DRY spec
Implement multiple goals for an experiment
rebase from upstream/master
DRY spec
fix some bugs
remove default goal
update readme