Buffering documents in the add method and remove them after is wrong

[lbdremy]

I implemented this a while ago, and it appears it's not a good idea.
If buffering is necessary it should be done outside of this method.

Case where it causes trouble:

var solr = require('solr-client');
var client1 = solr.createClient({host : 'localhost',port : 8983});
var client2 = solr.createClient({host: '12.67.78.98',port : 8983});
var docs = [ { id : 3938, title: 'blalbkjj'},{ id :78783, title : 'broubrou'}];
client1.add(docs,function(err,obj){});
client2.add(docs,function(err,obj){}); // Well, I'm sorry for you client2 but your array of docs is empty

The quick fix, without breaking the buffering feature in the add method would be to clean the array of docs only if this.updateEach !=1 and so add a condition where the splice is done
if(this.updateEach != 1){ this.adds.splice(0,this.adds.length); // Remove every elements}

I will remove the buffering feature and so this.adds, and the method flushAdd in the next minor release but for now I will just add this condition above.

[lbdremy]

Actually the suite test doesn't pass with this change, so let's drop this feature in the next release.