Update changelog.

Switch from netifaces to ifaddr. (WebThingsIO#50)

ifaddr is pure Python, so it doesn't require a toolchain like
netifaces does.

Handle tornado 6.X versions. (WebThingsIO#47)

Fixes WebThingsIO#46

Add support for Python 2.7 and 3.4. (WebThingsIO#41)

Fixes WebThingsIO#40

Update CHANGELOG.

Update CHANGELOG.

Validate property values with JSON schema validator. (WebThingsIO#31)

Fix typo.

Fixes WebThingsIO#29

Bump version.

Add better property value validation. (WebThingsIO#26)