generate 'version.py' file with plain version string instead of using pkg_resources to read version from package metadata

See https://github.com/fonttools/fonttools/issues/697#issuecomment-252621005

Lib/fontTools/version.py

@@ -1,4 +0,0 @@
-try:
-	__version__ = __import__('pkg_resources').require('fontTools')[0].version
-except Exception:
-	__version__ = 'unknown'

setup.py

@@ -42,9 +42,18 @@ fonts. The package also contains a tool called "TTX" which converts
 TrueType/OpenType fonts to and from an XML-based format.
 """
 
+version_template = """\
+# file generated by setuptools_scm
+# don't change, don't track in version control
+__version__ = {version!r}
+"""
+
 setup(
 	name="fonttools",
-	use_scm_version=True,
+	use_scm_version={
+		"write_to": "Lib/fontTools/version.py",
+		"write_to_template": version_template,
+	},
 	description="Tools to manipulate font files",
 	author="Just van Rossum",
 	author_email="just@letterror.com",