update to_html and wrote contributing guide

Author: v0dro

.gitignore

@@ -1,2 +1,2 @@
-daru-0.0.5.gem
+*.gem
 Gemfile.lock

CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing guide
+
+## Installing daru development dependencies
+
+If you want to run the full rspec suite, you will need the latest unreleased nmatrix and gsl-nmatrix ruby gems. They will released upstream soon but please follow this procedure for now.
+
+Keep in mind that either nmatrix OR gsl-nmatrix are NOT NECESSARY for using daru. They are just required for an optional speed up.
+
+To install dependencies, execute the following commands:
+
+  `export CPLUS_INCLUDE_PATH=/usr/include/atlas` 
+  `export C_INCLUDE_PATH=/usr/include/atlas`
+  `sudo apt-get update -qq`
+  `sudo apt-get install -qq libatlas-base-dev`
+  `sudo apt-get --purge remove liblapack-dev liblapack3 liblapack3gf`
+  `sudo apt-get install -y libgsl0-dev r-base r-base-dev`
+  `sudo Rscript -e "install.packages(c('Rserve','irr'),,'http://cran.us.r-project.org')"`
+
+Then execute the .build.sh script to clone and install the latest nmatrix and gsl-nmatrix on your system:
+
+  `./.build.sh`
+
+Then finally install remaining dependencies:
+
+  `bundle install`
+
+And run the test suite (should be all green with pending tests):
+
+  `bundle exec rspec`
+
+If you have problems installing nmatrix, please consult the [nmatrix installation wiki](https://github.com/SciRuby/nmatrix/wiki/Installation) or the [mailing list](https://groups.google.com/forum/#!forum/sciruby-dev).

Gemfile

@@ -1,5 +1,2 @@
 source 'https://rubygems.org'
 gemspec
-
-# gem 'gsl-nmatrix', :git => "https://github.com/v0dro/gsl-nmatrix.git", :ref => "763413625c39231e916cc6f38dfa0141598a9b80"
-gem 'gsl-nmatrix'

README.md

@@ -27,6 +27,7 @@ Written in pure Ruby so should work with all ruby implementations. Tested with M
 * Optional speed and space optimization on MRI with [NMatrix](https://github.com/SciRuby/nmatrix) and GSL.
 * Easy splitting, aggregation and grouping of data.
 * Quickly reducing data with pivot tables for quick data summary.
+* Import and exports dataset from and to Excel, CSV, Databases and plain text files.
 
 ## Notebooks
 

lib/daru/dataframe.rb

@@ -1684,9 +1684,10 @@ def to_html threshold=30
           (@vectors + 1).size.times { html += '<td>...</td>' }
           html += '</tr>'
 
-          last_row = self.row[size - 1]
+          last_index = @index.to_a.last
+          last_row = self.row[last_index]
           html += '<tr>'
-          html += "<td>" + @index[size-1].to_s + "</td>"
+          html += "<td>" + last_index.to_s + "</td>"
           (0..(ncols - 1)).to_a.each do |i|
             html += '<td>' + last_row[i].to_s + '</td>' 
           end