Documented new QtPy requirement

Author: PierreRaybaut

README.md

@@ -82,7 +82,7 @@ for more details on API limitations when comparing to Qwt.
 ### Requirements ###
 - Python >=2.6 or Python >=3.2
 - PyQt4 >=4.4 or PyQt5 >= 5.5
-- QtPy
+- QtPy >= 1.3
 - NumPy >= 1.5
 
 ## Installation

doc/installation.rst

@@ -7,7 +7,7 @@ Dependencies
 Requirements:
     * Python 2.x (x>=6) or 3.x (x>=2)
     * PyQt4 4.x (x>=3 ; recommended x>=4) or PyQt5 5.x (x>=5)
-    * QtPy
+    * QtPy >= 1.3
     * NumPy 1.x (x>=5)
     * Sphinx 1.x (x>=1) for documentation generation
 

setup.py

@@ -95,7 +95,7 @@ def get_subpackages(name):
     package_data={
         PACKAGE_NAME: get_package_data(PACKAGE_NAME, (".png", ".svg", ".mo"))
     },
-    install_requires=["NumPy>=1.5", "QtPy"],
+    install_requires=["NumPy>=1.5", "QtPy>=1.3"],
     extras_require={"Doc": ["Sphinx>=1.1"],},
     entry_points={
         "gui_scripts": [