changelog for v0.15.0

update CHANGELOG.md for 0.14.2

update CHANGELOG.md for 0.14.1

update CHANGELOG.md for 0.14.0

update CHANGELOG.md for 0.13.4

update CHANGELOG.md for 0.13.3

v0.13.2

This release contains major performance improvements for Spack environments, as well as some bugfixes and minor changes.

* allow missing modules if they are blacklisted (spack#13540)
* speed up environment activation (spack#13557)
* mirror path works for unknown versions (spack#13626)
* environments: don't try to modify run-env if a spec is not installed (spack#13589)
* use semicolons instead of newlines in module/python command (spack#13904)
* verify.py: os.path.exists exception handling (spack#13656)
* Document use of the maintainers field (spack#13479)
* bugfix with config caching (spack#13755)
* hwloc: added 'master' version pointing at the HEAD of the master branch (spack#13734)
* config option to allow gpg warning suppression (spack#13744)
* fix for relative symlinks when relocating binary packages (spack#13727)
* allow binary relocation of strings in relative binaries (spack#13724)

`spack find` now displays variants and other spec constraints

If you do this in a spack environment:

    spack add hdf5+hl

hdf5+hl will be the root added to the `spack.yaml` file, and you should
really expect `hdf5+hl` to display as a root in the environment.

- [x] Add decoration to roots so that you can see the details about what
      is required to build.
- [x] Add a test.

Add top-level `CHANGELOG.md` with release notes.

Merge branch 'releases/v0.12'