Make OpenVINO optional

Author: dkurt

README.md

@@ -40,6 +40,11 @@ $ source venv3/bin/activate
 (venv3) $ bonito download --models --latest
 ```
 
+To build with OpenVINO backend:
+```bash
+(venv3) $ pip install develop .[openvino]
+```
+
 ## Models
 
 The following pretrained models are available to download with `bonito download`.

requirements.txt

@@ -14,4 +14,3 @@ ont-fast5-api==3.3.0
 fast-ctc-decode==0.3.0
 cupy-cuda102==9.6.0
 genomeworks-cuda-10-2==2021.2.2
-openvino==2021.4.1

setup.py

@@ -43,6 +43,9 @@ def run(self):
     packages=find_packages(),
     include_package_data=True,
     install_requires=requirements,
+    extras_require = {
+        'openvino': ['openvino==2021.4.1'],
+    },
     long_description=long_description,
     long_description_content_type='text/markdown',
     author='Oxford Nanopore Technologies, Ltd',