Release 0.5.0

What's Changed

• Mark extends as simple by @veewee in #12
• Improve bottom type inference of nested simple types by @veewee in #13

<simpleType name="StringLength1to128">
    <restriction base="string">
	<minLength value="1"/>
	<maxLength value="128"/>
    </restriction>
</simpleType>
<complexType name="EmailType">
      <simpleContent>
          <extension base="tns:StringLength1to128">
              <attribute name="EmailType" type="string" use="optional" />
          </extension>
      </simpleContent>
</complexType>
<complexType name="VerificationType">
    <sequence>
	<element name="Email" type="tns:EmailType" minOccurs="0"></element>
    </sequence>
</complexType>

Types:
  > http://test-uri/:StringLength1to128 extends string
  > http://test-uri/:EmailType extends StringLength1to128 {
    StringLength1to128 $_
    @string $EmailType
  }
  > http://test-uri/:VerificationType {
    ?EmailType $Email
  }

Full Changelog: 0.3.0...0.5.0