Convenience plot() method on the ProvBundle class.

This makes interactive work much more convenient.
Fixing doc
Convenience read() method with a lazy format detection.

One can now just call prov.read() to the read a file.
Merge pull request #56 from krischer/convenience_read

Convenience read() method with a lazy format detection.
Merge pull request #55 from krischer/convenience_plot

Convenience `ProvDocument.plot()` function
Fixed: NamespaceManager.valid_qualified_name() did not support XSDQName
Fixed: py26's lack of assertIsInstance
Minor refactoring of test cases
Simplifying round-trip tests
Merge branch 'master' into prov-xml
Added test_attributes and test_statements for prov-xml
Merge pull request #1 from trungdong/prov-xml

Added test_attributes and test_statements for prov-xml