0.1.0

• Support parsing Fluent Syntax 0.3.
• Support formatting Messages and Attributes alike.
• Support string- and Number-typed external arguments
• Select expressions:
  • without a selector.
  • with literal strings and numbers as selector,
  • with external arguments as selector,
  • with message reference as selector (using tags).
• Support matching numbers in select expression to plural categories.
  • Only a single mock plural rule has been implemented for now.
• Support Attribute expressions.
• Support Variant expressions.
• MessageContext::new now takes a slice as the locales argument.
• Added integration with Travis CI and Coveralls.
• Expanded module documentation.