Update tox and appveyor for CI tests to exclude pytest < 3

Update the install requires versions for pytest

appveyor.yml

@@ -1,28 +1,13 @@
 environment:
   matrix:
   # note: please use "tox --listenvs" to populate the build matrix
-  - TOXENV: "py26-pytest27"
-  - TOXENV: "py26-pytest28"
-  - TOXENV: "py26-pytest29"
   - TOXENV: "py26-pytest30"
-  - TOXENV: "py27-pytest27"
-  - TOXENV: "py27-pytest28"
-  - TOXENV: "py27-pytest29"
   - TOXENV: "py27-pytest30"
-  - TOXENV: "py34-pytest27"
-  - TOXENV: "py34-pytest28"
-  - TOXENV: "py34-pytest29"
   - TOXENV: "py34-pytest30"
-  - TOXENV: "py35-pytest27"
-  - TOXENV: "py35-pytest28"
-  - TOXENV: "py35-pytest29"
   - TOXENV: "py35-pytest30"
-  - TOXENV: "py36-pytest27"
-  - TOXENV: "py36-pytest28"
-  - TOXENV: "py36-pytest29"
   - TOXENV: "py36-pytest30"
-  - TOXENV: "py27-pytest28-pexpect"
-  - TOXENV: "py35-pytest28-pexpect"
+  - TOXENV: "py27-pytest30-pexpect"
+  - TOXENV: "py35-pytest30-pexpect"
   - TOXENV: "flakes"
   - TOXENV: "readme"
 

setup.py

@@ -20,7 +20,7 @@ setup(
         ],
     },
     zip_safe=False,
-    install_requires=['execnet>=1.1', 'pytest>=2.7.0', 'py>=1.4.22'],
+    install_requires=['execnet>=1.1', 'pytest>=3.0.0', 'py>=1.4.22'],
     setup_requires=['setuptools_scm'],
     classifiers=[
         'Development Status :: 5 - Production/Stable',

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 # if you change the envlist, please update .travis.yml file as well
 envlist=
-  py{26,27,34,35,36}-pytest{27,28,29,30}
-  py{27,35}-pytest28-pexpect
+  py{26,27,34,35,36}-pytest{30}
+  py{27,35}-pytest{30}-pexpect
   flakes
   readme
 
@@ -14,9 +14,6 @@ deps =
   pycmd
   # to avoid .eggs
   setuptools_scm
-  pytest27: pytest~=2.7.2
-  pytest28: pytest~=2.8.7
-  pytest29: pytest~=2.9.2
   pytest30: pytest~=3.0.5
   pexpect: pexpect
 platform=