TODO

copy flag tests from mtail_test.sh

concatenate programs into a single vm instance, so that common matches can be
   collapsed, e.g. syslog matching.

standard library, search path

refactor fs and notify into single interface

no trailing newline in parser test, requires changes to expr stmt

float types for gauges

type checking

type inference?

type casting

parse tree/ast testing, s-expressions to render expected?

mapping between progs and logs to reduce wasted processing