Don't use pip to install into RTD env

Author: goerz

docs/rtd_environment.yml

@@ -9,3 +9,16 @@ dependencies:
   - pytest-xdist
   - coverage
   - flake8
+  - pip:
+    - argh
+    - better-apidoc>=0.1.4
+    - livereload
+    - pathtools
+    - port-for
+    - pyx>=0.14.1
+    - requests-toolbelt
+    - sphinx-autobuild
+    - tables
+    - tqdm
+    - twine
+    - watchdog

readthedocs.yml

@@ -8,7 +8,7 @@ build:
     image: latest
 python:
    version: 3.6
-   setup_py_install: false
-   pip_install: true
+   setup_py_install: true
+   pip_install: false
    extra_requirements:
         - dev