remove the E_Strict warning with php > 5.1

As of php 5.1 the use of mktime() yields a warning (see http://php.net/manual/en/function.mktime.php). This simple change should fix this and is the recommended fix by the php devs.
Removing those warnings really helps to keep the server logs nice and clean ;)
Created new output format HighCharts
Added Higcharts library as a submodule
Added frequency distribution chart
Refined Frequency Histogram
bugfix (value filter does not filter out all empty values)

Added a case for empty values
Update README.md
Create CONTRIBUTING.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
Update README.md
removed dupes
Added temporary solution for:
https://github.com/SemanticMediaWiki/SemanticResultFormats/issues/15
Added proper percentile function.
Added P90 and P10
Merge branch 'master' of https://github.com/netbrain/SemanticResultFormats