title: Concatenate strings from several rows using Pandas groupby
body: <p>I want to merge several strings in a dataframe based on a groupedby in Pandas. </p>
  
  <p>This is my code so far:</p>
  
  <pre><code>import pandas as pd
  from io import StringIO
  
  data = StringIO("""
  "name1","hej","2014-11-01"
  "name1","du","2014-11-02"
  "name1","aj","2014-12-01"
  "name1","oj","2014-12-02"
  "name2","fin","2014-11-01"
  "name2","katt","2014-11-02"
  "name2","mycket","2014-12-01"
  "name2","lite","2014-12-01"
  """)
  
  # load string as stream into dataframe
  df = pd.read_csv(data,header=0, names=["name","text","date"],parse_dates=[2])
  
  # add column with month
  df["month"] = df["date"].apply(lambda x: x.month)
  </code></pre>
  
  <p>I want the end result to look like this:</p>
  
  <p><img src="https://i.stack.imgur.com/xoEhO.png" alt="enter image description here"></p>
  
  <p>I don't get how I can use groupby and apply some sort of concatenation of the strings in the column "text". Any help appreciated!</p>