Add imgtool publishing support

This adds initial support for publishing imgtool to pypi.org.

The main imgtool.py was moved to imgtool package and made into the main
file, and a new imgtool.py that calls into the package, was added allowing
for the old usage behavior to remain functional.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/scripts/setup.py b/scripts/setup.py
new file mode 100644
index 0000000..0ec2cd9
--- /dev/null
+++ b/scripts/setup.py
@@ -0,0 +1,25 @@
+import setuptools
+
+setuptools.setup(
+    name="imgtool",
+    version="1.2.0",
+    author="The MCUboot commiters",
+    description=("MCUboot's image signing and key management"),
+    license="Apache Software License",
+    url="http://github.com/JuulLabs-OSS/mcuboot",
+    packages=setuptools.find_packages(),
+    install_requires=[
+        'cryptography>=2.4.2',
+        'intelhex>=2.2.1',
+        'click',
+    ],
+    entry_points={
+        "console_scripts": ["imgtool=imgtool.main:imgtool"]
+    },
+    classifiers=[
+        "Programming Language :: Python :: 3",
+        "Development Status :: 4 - Beta",
+        "Topic :: Software Development :: Build Tools",
+        "License :: OSI Approved :: Apache Software License",
+    ],
+)