Upgrade isort and set default dev interpreter to Python 3.8 (#602)

Update a few things related to the dev environment:
 * Set the default development interpreter version to Python 3.8. This should help improve startup times a bit to help iteration during development.
 * Lock dev dependencies again for Python 3.8. This resulted in updating isort to version 5.0, which produced a pretty significant diff (and made me break this PR out from #601). 
    * In so doing, I also took this opportunity to update a few places where I'd used `as keyword`, `as symbol`, and `as vector` import aliases rather than `as kw`, `as sym`, and `as vec` respectively. Should make it easier to contribute new code anywhere and not be surprised about the alias in use.

Author: chrisrink10

Makefile

@@ -19,7 +19,7 @@ docs:
 
 .PHONY: format
 format:
-	@pipenv run sh -c 'isort -rc . && black .'
+	@pipenv run sh -c 'isort --profile black . && black .'
 
 
 lispcore.py:

Pipfile

@@ -28,7 +28,7 @@ python-dateutil = "*"
 pytest = "*"
 
 [requires]
-python_version = "3.6"
+python_version = "3.8"
 
 [pipenv]
 allow_prereleases = true

Pipfile.lock

@@ -24,12 +24,6 @@ exclude = '''
 
 [tool.isort]
 known_first_party = 'basilisp'
-multi_line_output = 3
-include_trailing_comma = true
-force_grid_wrap = 0
-use_parentheses = true
-line_length = 88
-combine_as_imports = true
 skip = [
   '.env',
   '.hg',

pyproject.toml

@@ -1,5 +1,7 @@
 import sys
-from ast import (  # noqa
+from ast import Ellipsis  # pylint: disable=redefined-builtin
+from ast import slice  # pylint: disable=redefined-builtin
+from ast import (
     AST,
     Add,
     And,
@@ -31,7 +33,6 @@
     Dict,
     DictComp,
     Div,
-    Ellipsis,
     Eq,
     ExceptHandler,
     Expr,
@@ -64,7 +65,9 @@
     LtE,
     MatMult,
     Mod,
-    Module as _Module,
+)
+from ast import Module as _Module  # noqa
+from ast import (
     Mult,
     Name,
     NameConstant,
@@ -102,7 +105,9 @@
     YieldFrom,
     alias,
     arg,
-    arguments as _arguments,
+)
+from ast import arguments as _arguments
+from ast import (
     boolop,
     cmpop,
     comprehension,
@@ -121,7 +126,6 @@
     mod,
     operator,
     parse,
-    slice,
     stmt,
     unaryop,
     walk,

src/basilisp/_pyast.py

@@ -6,11 +6,11 @@
 import click
 import pytest
 
-import basilisp.lang.compiler as compiler
-import basilisp.lang.reader as reader
-import basilisp.lang.runtime as runtime
-import basilisp.lang.symbol as sym
-import basilisp.main as basilisp
+from basilisp import main as basilisp
+from basilisp.lang import compiler as compiler
+from basilisp.lang import reader as reader
+from basilisp.lang import runtime as runtime
+from basilisp.lang import symbol as sym
 from basilisp.prompt import get_prompter
 
 CLI_INPUT_FILE_PATH = "<CLI Input>"