added script to download and prepare sentiment data

sentiment/download_prepare.sh

+#!/bin/bash
+# file: prepare_data.sh
+#
+# Program: Downloads and prepares data containing the sentiment dataset.
+#
+# Author: Thomas Huetter
+
+# create target folder and change into it
+mkdir sentiment
+cd sentiment
+
+# download the data files
+wget https://nlp.stanford.edu/sentiment/trainDevTestTrees_PTB.zip
+
+# unzip the data into folder original_data
+unzip trainDevTestTrees_PTB.zip
+
+# remove zip file
+rm -rf trainDevTestTrees_PTB.zip
+
+# change to unzipped folder
+cd trees
+
+# prepare data for file L.trees
+# convert dev.txt and train.txt into UTF-8 format |   replace ( by {    |   replace ) by }    | sort by number of nodes (equivalent to number of "{")
+iconv -f ISO-8859-1 -t "UTF-8" dev.txt train.txt  | sed -e 's/(/{/g' | sed -e 's/)/}/g' | awk '{print gsub("{","{"), $0}' | sort -n  | cut -d' ' -f2- > ../sentiment.bracket
+
+# go back to the folder
+cd ..
\ No newline at end of file