Use sbt 0.13.0 to build the 0.13 branch.
Update versions in CONTRIBUTING
Docs: phase out mailing list as a support channel
Convert -classpath to CLASSPATH when forking on Windows and length exceeds a heuristic maximum.  Fixes #755.
Attempt to improve key collision error message
Move some logic in custom pom parser to separate methods
do custom pom processing when reading from cache, fixes #876
don't transform a module descriptor after it has already been processed by this sbt version.  Ref #876.
parse external pom.xml with CustomPomParser to handle multiple definitions.

Fixes #758.  This is the same issue fixed by 74c07c64a78447274be47804a6f5f5019c571dab
but in this case the cause was the top-level pom.xml, which didn't go through CustomPomParser.
Extra access methods for IPC
Recover from failed 'reload' command in the scripted sbt handler.
Pending test case for #805.
Docs: clean up Getting-Started/Basic-Def, including an example of defining a key.  Fixes #862.
The Process methods that are redirection-like should not discard the exit code of the input.

Only piping should do that.  This addresses an inconsistency with Fork, where using the CustomOutput
OutputStrategy makes the exit code always zero.
Docs: fix global plugins paths to include version in Getting-Started/Full-Def
Docs: update Direct Usage section of Forking page.  Closes #881.
Docs: use different local directory for ghpages repository for snapshots and stable updates.
String upper/lower case no longer locale dependent

Fixed many instances of the Turkish i bug.

Spare a thought for the poor Turks!
Restore sxr support and fix links to sxr'd sources.  Fixes #863.
Minimal support for class file formats 51.0, 52.0 in incremental compiler.  Fixes #842.

It is not currently possible to use a newer class file format than the one for the jvm sbt is running in.