Create addError() fn with parallel structure to addNotice
Highlight console.logs containing "Error" in red
Add error logging after notices.

This might not be the best place for this to log, if it even should,
in non-verbose modes.
Add a basic error reporting module.
Change addError => addJSError, this.error => this.jsError
Change `pageerror` event => `jsError` event
Remove instances of addJSError() fn
Rename: errors -> jserrors
Update README
Merge pull request #86 from macbre/page_errors_83

Page errors 83