Update HISTORY.md

Author: vinayak-mehta

.travis.yml

@@ -26,7 +26,7 @@ jobs:
       python: '3.7'
       dist: xenial
     - stage: coverage
-      python: 3.6
+      python: '3.6'
       script:
         - make test
         - codecov --verbose

HISTORY.md

@@ -7,6 +7,10 @@ master
 * Downgrade numpy version from 1.15.2 to 1.13.3.
 * Add requirements.txt for readthedocs.
 
+**Improvements**
+
+* Add Makefile and make codecov run only once. [#132](https://github.com/socialcopsdev/camelot/pull/132) by [Vaibhav Mule](https://github.com/vaibhavmule).
+
 **Documentation**
 
 * Add "Using conda" section to installation instructions.