Updates .travis.yml after some weird errors about installing from req…

…uirements.txt still.

.travis.yml

@@ -1,8 +1,10 @@
 language: python
 python:
   - "3.7.4"
+before_install:
+  - sudo apt-get -y install r-base
 install:
-  - pip install -r requirements.txt
+  - pip install .
   - pip install pytest pytest-cov coveralls
 script:
   - pytest --cov=kmerdb/