Update README.md

Fixed so build status is regarding master branch.
Merge pull request #50 from rOpenGov/api_fix

Package tests now integrated with travis during testing
Update pxweb.md

Added Linux mints and Fedora 20 prereqs.
Merge pull request #53 from rOpenGov/api_fix

Fix api errors
Merge pull request #54 from rOpenGov/master

Update branch