try to fix compilation on rtd

.readthedocs.yml

@@ -0,0 +1,13 @@
+version: 2
+
+sphinx:
+  configuration: source/conf.py
+
+python:
+  version: 3.5
+  install:
+    - requirements: requirements.txt
+    - method: pip
+    
+
+

requirements.txt

@@ -1 +1,13 @@
-#git+https://github.com/fabpot/sphinx-php.git@52f7bd2216cc22ef52494f346c5643bb2a74513f#egg=sphinx-php
+alabaster==0.7.10
+Babel==2.4.0
+docutils==0.13.1
+imagesize==0.7.1
+Jinja2==2.10.1
+MarkupSafe==1.0
+Pygments==2.2.0
+pytz==2017.2
+requests==2.20.0
+six==1.10.0
+snowballstemmer==1.2.1
+Sphinx==1.3.6
+git+https://github.com/fabpot/sphinx-php.git@7312eccce9465640752e51373a480da700e02345#egg_name=sphinx-php