[enh] #66: Add pyproject.toml file

pyproject.toml

+[tool]
+[tool.poetry]
+name = "duniterpy"
+version = "0.56.0"
+description = "Python library for developers of Duniter clients"
+authors = ["inso <insomniak.fr@gmail.com>", "canercandan", "s_b"]
+maintainers = ["vit <vit@free.fr>", "Moul <moul@moul.re>"]
+readme = "README.md"
+license = "GPL-3.0-or-later"
+homepage =  ""
+repository = "https://git.duniter.org/clients/python/duniterpy"
+documentation = "https://clients.duniter.io/python/duniterpy/index.html"
+keywords = ["g1", "duniter", "cryptocurrency", "librecurrency", "library"]
+classifiers = [
+    "Development Status :: 5 - Production/Stable",
+    "Natural Language :: English",
+    "Operating System :: OS Independent",
+    "Topic :: Software Development :: Libraries",
+    "Intended Audience :: Developers",
+]
+
+[build-system]
+requires = ["poetry>=0.12"]
+build-backend = "poetry.masonry.api"
+
+[tool.poetry.dependencies]
+python = "^3.5.3"
+aiohttp = "^3.6.1"
+jsonschema = "^3.0.2"
+pypeg2 = "^2.15.2"
+attrs = "^19.3.0"
+base58 = "^1.0.3"
+pylibscrypt = "^1.8.0"
+libnacl = "^1.6.1"
+pyaes = "^1.6.1"
+
+[tool.poetry.dev-dependencies]
+black = { version = "^19.3b0", python = "^3.6" }
+mypy = "^0.730"
+pylint = "^2.4.2"
+sphinx = "^2.3.1"
+sphinx_rtd_theme = "^0.4.3"