Use --no-deps on model install

In general, it's nice for models to specify spaCy as a dependency. However, this tends to cause problems in conda environments, as pip will re-install spaCy and its dependencies (especially Thinc)

spacy/cli/download.py

@@ -84,5 +84,5 @@ def get_version(model, comp):
 def download_model(filename):
     download_url = about.__download_url__ + '/' + filename
     return subprocess.call(
-        [sys.executable, '-m', 'pip', 'install', '--no-cache-dir',
+        [sys.executable, '-m', 'pip', 'install', '--no-cache-dir', '--no-deps',
          download_url], env=os.environ.copy())