title: Shiny/Leaflet map not rendering
body: <p>I can't get a leaflet map to render in my shiny app, although the code works by itself outside of shiny. I do not get any errors so I am stuck, any help is appreciated.</p>
  
  <p>Sample Data:</p>
  
  <pre><code>cleanbuffalo &lt;- data.frame(name = c("queen","toni","pepper"), 
                             longitude = c(31.8,32,33), 
                             latitude = c(-24,-25,-26))
  </code></pre>
  
  <p>Shiny UI:</p>
  
  <pre><code>vars &lt;- c(
    "Pepper" = "pepper",
    "Queen" = "queen",
    "Toni" = "toni"
  )
  
  shinyUI(navbarPage("Buffalo Migration", id ="nav",
  
    tabPanel("Interactive Map",
  
  div(class="outer",
  
      leafletOutput("map", width = "100%", height = "100%"),
      #Panel Selection
      absolutePanel(id = "controls", class = "panel panel-default", fixed = TRUE,
        draggable = TRUE, top = 60, left = "auto", right = 20, bottom = "auto",
        width = 330, height = "auto",
  
        h2("Buffalo Migration"),
        #Buffalo Group selection
        checkboxGroupInput(
          "checkGroup", label = h3("Select Buffalo to Follow"),
          choices = vars,
          selected = 1)
            )
          )
        )
    )
  )
  </code></pre>
  
  <p>Shiny Server:</p>
  
  <pre><code>library(shiny)
  library(dplyr)
  library(leaflet)
  library(scales)
  library(lattice)
  
  shinyServer(function(input, output, session) {
    output$map &lt;- renderLeaflet({
      leaflet() %&gt;% addTiles() %&gt;% setView(lng = 31.88, lat = -25.02, zoom=1)
    })
  </code></pre>