add tiny server for running tests locally

This avoids the security restrictions on web workers over file://.
Merge pull request #124 from bluej100/localtests

add tiny server for running tests locally
Updated README
add build command
Merge pull request #127 from bluej100/build

add build command
provide current cursor to step callback
use parser to find last row end in chunks
Merge pull request #125 from bluej100/progress

provide current cursor to step callback
Merge pull request #135 from bluej100/chunkboundary

use parser to find last row end in chunks
allow aborting workers