v0.9.0: out with --out, in with stdout

new features

• --out is now optional; if not specified, the section will be rendered to
  stdout.

• --tag has been added; if specified, the section will be loaded and then
  only the section specified by the given tag will be rendered.

misc

• the 'unknown template for (TYPE)' error condition is now returned earlier and
  returns an error specifying the name of the missing template.

• added a joinLines function, which is useful for implementing Markdown-style
  syntax where all lines but the first have to be inteded (e.g. lists).