added test for #241
Merge pull request #244 from rs/fix-zip-source

Fix ZipSource exception about binary mode not supported (fix #241)
Merge branch 'master' of github.com:alimanfoo/petl
tweak test for #241; closes #241
closes #238
closes #237
closes #236
closes #235
closes #233
closes #232
closes #220
closes #214
closes #171
v0.23
increment version
minor doco
travis
add tmp folder for testing files
add travis image
doco: fix travis image