Update travis ci badge to svg

A tiny pr that updates the travis ci badge to use svg instead
of png.
Relax required version of request_store
Merge pull request #637 from finalist/update-request-store

Relax required version of request_store
Merge pull request #633 from Adam89/ma-update-travis-badge-to-svg

Update travis ci badge to svg
Bumped version for looser request_store version