chore: add black and flake8 as pre-commit hook

.flake8

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+[flake8]
+ignore = E203, E266, E501, W503, F403, F401, B009, B011, C812, E741, PIE781, SFS101, SFS301
+max-line-length = 79
+max-complexity = 18
+select = B,C,E,F,W,T4,B9
+inline-quotes = double

.pre-commit-config.yaml

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+repos:
+-   repo: https://github.com/psf/black
+    rev: 19.3b0
+    hooks:
+    -   id: black
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.5.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-docstring-first
+    -   id: check-yaml
+    -   id: debug-statements
+    -   id: double-quote-string-fixer
+    -   id: name-tests-test
+    -   id: requirements-txt-fixer
+    -   id: check-json
+    -   id: debug-statements
+    -   id: end-of-file-fixer
+        files: \.py$
+-   repo: https://gitlab.com/pycqa/flake8
+    rev: 3.8.0
+    hooks:
+    -   id: flake8
+        additional_dependencies: [
+            'flake8-blind-except',
+            'flake8-bugbear',
+            'flake8-comprehensions',
+            'flake8-docstrings',
+            'flake8-implicit-str-concat',
+            'flake8-quotes',
+            'flake8-rst-docstrings',
+            'pydocstyle>=5.0.0',
+        ]

pre-commit_documentation.md

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+## Integrating black and flake8 as pre-commit hook
+
+Black and flake8 are two of the most important code formatters. This ensures that every code is well formatted and organized.
+
+### Setting up the pre-commit hook
+##### What does this pre-commit hook do ?
+This pre-commit hook ensures that the code is well formatted before a commit is made.
+
+##### Steps to run this pre-commit hook
+1. Update your local, cloned repository
+```bash
+$ git pull upstream <branch-name>
+```
+2. Move the file named : ```pre-push``` to ```.git``` folder.
+3. Install the git hook
+```bash
+$ pre-commit install
+```
+###### NOTE: In case you do not have pre-commit,you can simply pip install it and then run step 2.
+```bash
+pip install pre-commit
+```
+4. Now stage your changes and commit them. You will see that the checks will run automatically.
+5. If you check the status, you will the code related files have been modified automatically.
+```bash
+$ git status
+```
+If you go and check the files on your local machine/editor, you will see that the code has been formatted.
+6. Stage the modified files and follow the normal steps for generating a pull request.
+```bash
+$ git add <file-name>
+...
+$ git commit -m "<commit message>" --no-verify
+...
+$ git push origin <branch-name>
+```

pre-push

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+#!/bin/bash
+
+if [ -f .git/hooks/pre-commit ];
+then
+    exit 0
+else
+    echo "Unstage changes and install pre-commit first(COMMAND : $ pre-commit install). Then commit."
+    exit 1
+fi

pyproject.toml

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+[tool.black]
+line-length = 79
+include = '\.pyi?$'
+exclude = '''
+/(
+    \.git
+  | \.hg
+  | \.mypy_cache
+  | \.tox
+  | \.venv
+  | _build
+  | buck-out
+  | build
+  | dist
+)/
+'''