Added docs on reporters

docs/reporters.md

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+# Reporters
+
+Catch has a modular reporting system and comes bundled with a handful of useful reporters built in.
+You can also write your own reporters.
+
+## Using different reporters
+
+The reporter to use can easily be controlled from the command line.
+To specify a reporter use [`-r` or `--reporter`](command-line.md#choosing-a-reporter-to-use), followed by the name of the reporter, e.g.:
+
+```
+-r xml
+```
+
+If you don't specify a reporter then the console reporter is used by default.
+There are four reporters built in to the single include:
+
+* `console` writes as lines of text, formatted to a typical terminal width, with colours if a capable terminal is detected.
+* `compact` similar to `console` but optimised for minimal output - each entry on one line
+* `junit` writes xml that corresponds to Ant's [junitreport](http://help.catchsoftware.com/display/ET/JUnit+Format) target. Useful for build systems that understand Junit. 
+Because of the way the junit format is structured the run must complete before anything is written. 
+* `xml` writes an xml format tailored to Catch. Unlike `junit` this is a streaming format so results are delivered progressively.
+
+There are a few additional reporters, for specific build systems, in the Catch repository (in `include\reporters`) which you can `#include` in your project if you would like to make use of them.
+Do this in one source file - typically the same one you have `CATCH_CONFIG_MAIN` or `CATCH_CONFIG_RUNNER`.
+
+* `teamcity` writes the native, streaming, format that [TeamCity](https://www.jetbrains.com/teamcity/) understands.
+Use this when building as part of a TeamCity build to see results as they happen.
+* `tap` writes in the TAP ([Test Anything Protocol](https://en.wikipedia.org/wiki/Test_Anything_Protocol)) format.
+* `automake` writes in a format that correspond to [automake  .trs](https://www.gnu.org/software/automake/manual/html_node/Log-files-generation-and-test-results-recording.html) files
+
+You see what reporters are available from the command line by running with `--list-reporters`.
+
+By default all these reports are written to stdout, but can be redirected to a file with [`-o` or `--out`](command-line.md#sending-output-to-a-file)
+
+## Writing your own reporter
+
+You can write your own custom reporter and register it with Catch.
+At time of writing the interface is subject to some changes so is not, yet, documented here.
+If you are determined you shouldn't have too much trouble working it out from the existing implementations -
+but do keep in mind upcoming changes (these will be minor, simplifying, changes such as not needing to forward calls to the base class).
+
+---
+
+[Home](Readme.md)