Local variables in flows and filter out $[0-9]{4} escapes

Major changes in this release are the introduction of local variables in flows #55 and strict filtering of invalid unicode escape sequences endemic to Freebase #61, as well as reliability and quality improvements such as #66 and #62. Although it's not reflected in the open source code, progress has been made on :BaseKB Now productization #59 in the sense that there is now an RSS feed.

See the matching milestone for a complete list of changes.