Added dismissalert to remove arbitrary number of messages

[dipterix]

This PR is related to issue #29

A simple demo showing how it works:

library(shiny)

ui <- fluidPage(
  shinyalert::useShinyalert(),
  actionButton('a','Ok')
)

server <- function(input, output, session) {
  observeEvent(input$a, {
    shinyalert::shinyalert(
      'Warning',
      'Click OK to run code',
      callbackR = function(...){
        # procedure 1 runs for 3~4 seconds
        Sys.sleep(3 + runif(1))
        # Now dismiss modal
        shinyalert::dismissalert()
      }
    )
    shinyalert::shinyalert(
      'Scheduled!',
      'R is running, please wait for the result...', 
      showConfirmButton = FALSE
    )
  })
}

shinyApp(ui, server)

[dipterix]

Changes:

1. Renamed dismissalert to closeAlert
2. Added immediate option to shinyalert
3. closeAlert can choose number of alerts to be closed, or a specific alert with cbid given
4. Fixed some pre-existing doc issues.

I added myself to DESCRIPTION as ctb (contributor, providing piece of code) as convention, you can remove it if it causes some legal issues.

[daattali]

I made a commit that uses uuid instead of hashing the params, so that's not an issue anymore. Thanks for bringing this to my attention

[daattali]

@dipterix let me know if you plan on continuing this or if I should take over!

[dipterix]

I got fever. Please go ahead make changes if you feel necessary.

[daattali]

I'm working on some other packages this week, if you don't finish the PR by the end of the month I'll try to finish it :)

[daattali]

@dipterix Are you able to finish this PR?

[daattali]

I actually went through all your code and I'm mostly done integrating it. I might ask you for a PR soon :)

[dipterix]

Hi @daattali , sorry for the late reply. The conflicts have been resolved.

[daattali]

Merged in #37