Added link to the tools list from the feeding-carbon documentation because that is another great way to get metrics into Carbon. Added entry for txCarbonClient to the tools list.
Add mapSeries and reduceSeries render functions

Currently, graphite has no way to map-reduce disparate series together
which is desirable for series that come from collectd and others
where calculations need to be performed on two or more related series.

This commit adds two new render functions: mapSeries and reduceSeries.
This is a generic way of mapping several related series together and
reducing them with another function.

- Add mapSeries function which takes a seriesList and maps it to a
  list of sub-seriesList. Each sub-seriesList has the given mapNode
  in common.
- Add reduceSeries function which takes a list of seriesLists and
  reduces it to a list of series by means of the reduceFunction.
- Add mock module to .travis.yml
- Add tests for mapSeries and reduceSeries
Revert "Added link to the tools list from the feeding-carbon documentation because that is another great way to get metrics into Carbon. Added entry for txCarbonClient to the tools list."

This reverts commit 05f925a1dca1e39251cb8db5917526b1c500beaf.
Merge remote-tracking branch 'parent/master'
Split up the documentation for the tools and the APIs into separate pages and link to them from the feeding carbon page. Add a link to txCarbonClient on the APIs page.
Merge pull request #578 from justenwalker/map-reduce-functions

Add mapSeries and reduceSeries render functions
Merge branch 'pr/469'

Closes #469