Remove use of `indexOf()` when adding locale data

`Array.prototype.indexOf()` is an ES5 method we were using when it
wasn't necessary. This remove its usage, and improves the error
handling when adding locale data and resolve locales.

Fixes #76
Use `hop` instead of `in` for safety
Merge pull request #77 from ericf/rm-indexof

Remove use of `indexOf()` when adding locale data
Peg intl-messageformat-parser to latest version
Update build to produce source map for dist/intl-messageformat.min.js
Build for 1.0.0-rc-6
1.0.0-rc-6
Update grunt-extract-cldr-data to fix plural rule bug in data
Re-build with fixed CLDR plural rule data
Improve error messages
Merge pull request #78 from ericf/fix-cldr-plural-data

Fix CLDR plural data