Breaking changes:
-----------------

* pin_downstream has been renamed to run_exports  #1911
* exclude_from_build_hash has been renamed to ignore_version  #1911

Enhancements:
-------------

* use rm_rf to remove prefixes for more cleanliness and better speed  #1915
* add support for multiple sources in one meta.yaml  #1929
* allow ``exact`` keyword for pin_compatible jinja2 function  #1929
* allow selectors in variant conda_build_config.yaml files  #1937

Bug fixes:
----------

* fix mmap/file problems on virtualbox shared folders  #1914
* Correct rendering with --dirty flag if recipe name appears as substring of another's name  #1931
* don't set language env vars (PERL, R, LUA, PYTHON) when those packages are not installed  #1932
* exclude language env vars from variant being set  #1944