Added StandardDeviationKeyVal operator and test class.
SPOI-1182 -

Added the Filter operator that can filter the key-value pairs based on the given filter. The keys in the KeyValuePair has to be implement a Filterable interface.

Also added required test cases.
Merge branch 'SPOI-1182'
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of https://github.com/DataTorrent/Malhar
added install script for front
Merge branch 'master' of https://github.com/DataTorrent/Malhar
#MLHR-835 #comment Fixed the file path issue, read the sample text file from the classpath.
#MLHR-835 #comment Added duration for the test case.
#MLHR-835 #comment Also fixed an issue with Twitter Rolling Top Words application. Most of the code was commented.
#MLHR-835 #comment Added log file and sample text file for Map-Reduce applications.
Merge branch 'master' of https://github.com/DataTorrent/Malhar
#MLHR-872 #comment Added demo guides for Twitter Top URL Counter, Twitter Rolling Top Words and Word Count Apps.
Demo guide for Pi application. #MLHR-915
Demo guide for PiCalculator demo application. #MLHR-915
Demo guide for Mobile demo application. #MLHR-915
removed console.log call
Installer texts corrected
Merge pull request #790 from davidyan-malhar/installer_text_fix

Installer texts corrected
fixed MLHR-924