Implementation of Coursera's assignment

# This script should be run with the data provided by
# Davide Anguita, Alessandro Ghio, Luca Oneto, Xavier Parra and Jorge
L. Reyes-Ortiz.
# Human Activity Recognition on Smartphones using a Multiclass
Hardware-Friendly Support Vector Machine.
# International Workshop of Ambient Assisted Living (IWAAL 2012).
Vitoria-Gasteiz, Spain. Dec 2012
# It merges information from various .txt files and creates a clean
data set according to Coursera's
# requiremens on Getting and Cleaning Data. It finally, saves the tidy
data set as tidy_data.csv