update CHANGELOG.md for 0.14.2

CHANGELOG.md

+# v0.14.2 (2019-04-15)
+
+This is a minor release on the `0.14` series. It includes performance
+improvements and bug fixes:
+
+* Improvements to how `spack install` handles foreground/background (#15723)
+* Major performance improvements for reading the package DB (#14693, #15777)
+* No longer check for the old `index.yaml` database file (#15298)
+* Properly activate environments with '-h' in the name (#15429)
+* External packages have correct `.prefix` in environments/views (#15475)
+* Improvements to computing env modifications from sourcing files (#15791)
+* Bugfix on Cray machines when getting `TERM` env variable (#15630)
+* Avoid adding spurious `LMOD` env vars to Intel modules (#15778)
+* Don't output [+] for mock installs run during tests (#15609)
+
 # v0.14.1 (2019-03-20)
 
 This is a bugfix release on top of `v0.14.0`.  Specific fixes include: