Upgrade to latest version of node-sass

[apalanki]

• This would allow support for Node 10.x and 11.x versions
• I tested this with those versions of node and it works as expected

[apalanki]

The Travis build needs to be updated to do the checks for latest versions of node.

[GeeWee]

npm audit has an outstanding security vulnerabillity on node-sass-middleware, hopefully updating this dependency will fix it:

  High            Arbitrary File Overwrite                                      
                                                                                
  Package         tar                                                           
                                                                                
  Patched in      >=4.4.2                                                       
                                                                                
  Dependency of   node-sass-middleware                                          
                                                                                
  Path            node-sass-middleware > node-sass > node-gyp > tar             
                                                                                
  More info       https://npmjs.com/advisories/803                              

[nschonni]

@apalanki since the ^ is already there, NPM will already install 4.11 on install (and 4.12 once it is released)

@GeeWee that is being tracked by sass/node-sass#2625 and tracing down to the Tar repo, it looks like 2.x tar isn't actually vulnerable like the report indicates, but is buggy