Allow installation of ML free version.

Add an option to the install script, `--no-ml`, that when given will
install Talon without ML support.

Fixes #96

MANIFEST.in

@@ -1,5 +1,3 @@
-recursive-include tests *
-recursive-include talon *
 recursive-exclude tests *.pyc *~
 recursive-exclude talon *.pyc *~
 include train.data

setup.py

@@ -1,4 +1,30 @@
 from setuptools import setup, find_packages
+from setuptools.command.install import install
+
+
+class InstallCommand(install):
+    user_options = install.user_options + [
+        ('no-ml', None, "Don't install without Machine Learning modules."),
+    ]
+
+    boolean_options = install.boolean_options + ['no-ml']
+
+    def initialize_options(self):
+        install.initialize_options(self)
+        self.no_ml = None
+
+    def finalize_options(self):
+        install.finalize_options(self)
+        if self.no_ml:
+            dist = self.distribution
+            dist.packages=find_packages(exclude=[
+                'tests',
+                'tests.*',
+                'talon.signature',
+                'talon.signature.*',
+            ])
+            for not_required in ['numpy', 'scipy', 'scikit-learn==0.16.1']:
+                dist.install_requires.remove(not_required)
 
 
 setup(name='talon',
@@ -10,7 +36,10 @@ setup(name='talon',
       author_email='admin@mailgunhq.com',
       url='https://github.com/mailgun/talon',
       license='APACHE2',
-      packages=find_packages(exclude=['tests']),
+      cmdclass={
+          'install': InstallCommand,
+      },
+      packages=find_packages(exclude=['tests', 'tests.*']),
       include_package_data=True,
       zip_safe=True,
       install_requires=[

talon/__init__.py

@@ -1,7 +1,12 @@
 from talon.quotations import register_xpath_extensions
-from talon import signature
+try:
+    from talon import signature
+    ML_ENABLED = True
+except ImportError:
+    ML_ENABLED = False
 
 
 def init():
     register_xpath_extensions()
+    if ML_ENABLED:
         signature.initialize()