Improved installation and no_ns methods

Thanks go to @wetneb, @anwaralameddin, @rudolphfroger, @jcamiel, @imcsk8 for contributions to this release.

Added

• Node methods: get_property_no_ns (alias: get_attribute_no_ns), get_properties_ns (alias: get_attributes_ns), has_property_no_ns (alias: has_attribute_no_ns), remove_property_no_ns (alias: remove_attribute_no_ns), get_property_node_ns (alias: get_attribute_node_ns), get_property_node_no_ns (alias: get_attribute_node_no_ns)
• Added implementations of Hash, PartialEq and Eq traits for Namespace

Changed

• Call bindgen at build time on Unix platforms (thanks @wetneb)