Add accessor functions for values

We can now do to a single value what we can do to an iterator position: query
its type and extract its value in C form.

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Use new accessor functions in parser_test

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Remove ason_create_number

The parser doesn't use this, and since we no longer expose it, it is now dead
code.

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Update manpages for API changes

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Add overview manpage

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Remove blockfile/btree code

We'll probably add this back later, but for now, it's not going into the
release so let's clean it out of the codebase.

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Remove dead code from output.c

This is useful stuff, but it all pertains to printing values that reduction
always removes before we need them. For this next release, we're killing it.

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>
Release 0.1

The NEWS.md update has a bit more to say, but this is the first semi-usable
release. Tag it and ship it!

Signed-off-by: Casey Dahlin <casey.dahlin@gmail.com>