Clean warning at bootstrap
write-to-string is available at host via !write-to-string
Newlines after semicolons if *PRETTY-PRINT* is set.

This is meant as a start to get more managable Javascript output, i.e.
while debugging in Firefox.
Simpler printer
Merge pull request #142 from Ferada/pretty-print

Newlines after semicolons if *PRETTY-PRINT* is set.
Execute tests asynchronously to let the browser to render
Revert asynchronous tests