add and use source for online look up
Use an own source for every online dict
revert last commit; use candidates for sources instead
delete `helm-dictionary-make-lookup-fun' (not needed anymore)
Unquote some lambdas
minor change
Simplified definition of helm-dictionary-source-online
Added nohighlight to helm-dictionary-source-online.
Use browse-url to access online dictionaries.
Added documentation for online dictionaries.
Allow customizing the browser function for opening online dictionaries.
Updated documentation on browser functions.
Changed opening of URLs according to Michael's suggestions.

Now, the customization variable `helm-dictionary-browser-function' can be set
to any value that is admissible for `browse-url-browser-function'.  The default behavior is to use `browse-url-browser-function'.
Fixing the browser-mess.

If the variable helm-dictionary-browser-function is nil, the currently
configured standard browser for browse-url is used.  Other admissible values
are the same as for browse-url-browser-function.
Fixed type of default setting for helm-dictionary-browser-function.

Also replaced tabs by spaces for consistency with the rest of the code.
Extended documentation, added commentary section for MELPA.
Add emacs-w3m to the lists of browsers.
Added helm's default browser to the list of browsers.
Use helm's facilities for opening URLs

instead of `browse-url`.
Added Michael to the list of authors.