Expand tabs with click on name. Fix #103

[lenafm]

Just had a look at this and it looks like all the modals are working fine and the panels are opening and collapsing as expected.

I tried all the controls in the example apps and noticed two things that don't seem to work. It looks like this has nothing to do with the changes you made as they don't work on the current master branch either:

• in the basic-app.R example, the plot in the second panel isn't created and an error is raised when has the collapsed = TRUE, even after opening the panel. It's fine when collapsed = FALSE and can then be collapsed and reopened without any problems.
• in the custom-css.R example, the shinypanels::box element only works properly when called directly in the UI. In the example, the box in the second panel is called from renderUI and it doesn't open (no matter if collapsed = TRUE or collapsed = FALSE).

Let me know if you want me to open two separate new issues for those things.

[ddazal]

Great. About the errors, please open new issues so we can discuss about them in the next sprint.