readme touchups
remove demo/test files which were moved to tests/python_tests in c84ddc825e4105445de4a - refs #1460
fix cairo reference counting and add more cairo context tests - closes #2031
travis: start testing cairo+pycairo+sqlite+postgres
xadd more cairo test files, replace existing via ubuntu saucy
Merge branch '2.3.x' of github.com:mapnik/mapnik into 2.3.x
tests: looser tolerance for comparing cairo output sizes
tests: stop testing cairo postscript output since it is not important
add #2031 fix to changelog
tests: lessen strictness of cairo comparison tests so that files created on ubuntu saucy/os x pass on ubuntu precise - refs #1868
merge with 2.3.x