Implement serialization of statements on properties.
Implement deserialization of statements on properties.
Update .travis.yml
Merge pull request #86 from wmde/statements-on-properties

Statements on properties
Correct @covers annotation.
Merge pull request #87 from wmde/correct-covers

Correct @covers annotation.
Add OPTION_OBJECTS_FOR_MAPS.

This will be useful when serializing to JSON to avoid putting out empty maps as
empty lists.
Merge pull request #89 from wmde/fix-empty-map-v2

Add OPTION_OBJECTS_FOR_MAPS.
Update .travis.yml
Don't use Statement class alias

Bug: 71508
Merge pull request #90 from wmde/evilclassalias

Don't use Statement class alias
Change construction of Statement with a Snak parameter.

In WikibaseDataModel 2.0 it is not directly supported anymore thus wrap it in a
Claim.
Merge pull request #91 from wmde/data-model-2.0

Upgrade to data-model 2.0
Test ClaimDeserializer with invalid type of QualifiersOrder.
Test TypedSnakSerializer with unsupported object.
Merge pull request #93 from wmde/coverage

Impove coverage
Replace References with ReferenceList.

This also means replacing ReferencesDeserializer.
Upgrade composer dependencies.
Merge pull request #92 from wmde/data-model-2.0

Upgrade to data-model 2.0
Release notes for 1.2.0