Update dependencies in setup.py

Specified minimum version of arrow and forced pulling
backports.shutil_get_terminal_size for python versions < 3.3.

setup.py

@@ -31,11 +31,16 @@ setup(
     url = "https://github.com/bram85/topydo",
     install_requires = [
         'six >= 1.9.0',
-        'arrow',
+        'arrow >= 0.7.0',
     ],
     extras_require = {
         ':sys_platform=="win32"': ['colorama>=0.2.5'],
-        ':python_version=="2.7"': ['ushlex'],
+        # shutil.get_terminal_size() was introduced in Python 3.3
+        ':python_version=="2.7"': [
+            'backports.shutil_get_terminal_size>=1.0.0',
+            'ushlex',
+        ],
+        ':python_version=="3.2"': ['backports.shutil_get_terminal_size>=1.0.0'],
         'ical': ['icalendar'],
         'prompt-toolkit': ['prompt-toolkit >= 0.53'],
         'edit-cmd-tests': ['mock'],