Enable dirty flag

For files that don't support as-you-type but are loaded by live HTML
documents (e.g. JS files), we want to show a dirty indicator on the
live development icon when they have unsaved changes, so the user knows
s/he needs to save in order to have the page reload.
add support for document change

Allow switching HTML documents and restart the live dev session on the
same browser.
Merge pull request #18 from sebaslv/dirty-flag

Enable dirty flag for JS files
update jsdoc
Merge pull request #19 from sebaslv/doc-change

add support for document change