Adding i18n support - Fixes #2

I've been needing this functionality and saw that there was already a ticket open for it here, so this is implementing it.

We basically just need to add options for the --locales and --messageFilePathFormat options of SoyToJsSrcCompiler.jar, and use them.

I added a unit test for this and it works well :)
Allow compiling multiple locales at the same time
Source formatting
Merge pull request #26 from mairatma/i18n

Adding i18n support - Fixes #2