Squashed 'packages/mr/' changes from 96d6276..bec7461

fd9abf8 0.15.3
6d1baf6 Merge pull request #72 from francoisfrisch/revert-sourcemap
ae86b0d Revert "Use sourceMappingURL instead of sourceURL"

git-subtree-dir: packages/mr
git-subtree-split: bec7461f86c4b86265bc847a0aa4e43cd6733214
Update Mr to v0.15.3
Merge pull request #1430 from Stuk/mr0.15.3

Mr v0.15.3