Update dependencies cli-helpers, prompt-toolkit, and sqlparse.

mssql-cli depends on old version of cli-helpers, prompt-toolkit, and sqlparse, which are incompatible with the newer versions that are required by pgcli 3.0.0. Is it possible to update these libraries?

```
ERROR: pgcli 3.0.0 has requirement cli-helpers[styles]>=1.2.0, but you'll have cli-helpers 0.2.3 which is incompatible.
ERROR: pgcli 3.0.0 has requirement prompt-toolkit<4.0.0,>=3.0.0, but you'll have prompt-toolkit 2.0.10 which is incompatible.
ERROR: pgcli 3.0.0 has requirement sqlparse<0.4,>=0.3.0, but you'll have sqlparse 0.2.4 which is incompatible.
```

**Full output**
```
> pip install mssql-cli
Defaulting to user installation because normal site-packages is not writeable
Requirement already satisfied: mssql-cli in ./.local/lib/python3.8/site-packages (1.0.0)
Requirement already satisfied: humanize>=0.5.1 in ./.local/lib/python3.8/site-packages (from mssql-cli) (2.4.0)
Requirement already satisfied: configobj>=5.0.6 in ./.local/lib/python3.8/site-packages (from mssql-cli) (5.0.6)
Collecting cli-helpers<1.0.0,>=0.2.3
Using cached cli_helpers-0.2.3-py2.py3-none-any.whl (26 kB)
Requirement already satisfied: enum34>=1.1.6 in ./.local/lib/python3.8/site-packages (from mssql-cli) (1.1.10)
Requirement already satisfied: future>=0.16.0 in /usr/lib/python3/dist-packages (from mssql-cli) (0.18.2)
Requirement already satisfied: wheel>=0.29.0 in /usr/lib/python3/dist-packages (from mssql-cli) (0.34.2)
Requirement already satisfied: applicationinsights>=0.11.1 in ./.local/lib/python3.8/site-packages (from mssql-cli) (0.11.9)
Collecting prompt-toolkit<2.1.0,>=2.0.0
Using cached prompt_toolkit-2.0.10-py3-none-any.whl (340 kB)
Requirement already satisfied: Pygments>=2.0 in ./.local/lib/python3.8/site-packages (from mssql-cli) (2.6.1)
Collecting sqlparse<0.3.0,>=0.2.2
Using cached sqlparse-0.2.4-py2.py3-none-any.whl (38 kB)
Requirement already satisfied: click<7.1,>=4.1 in ./.local/lib/python3.8/site-packages (from mssql-cli) (7.0)
Requirement already satisfied: argparse>=1.2.1 in ./.local/lib/python3.8/site-packages (from mssql-cli) (1.4.0)
Requirement already satisfied: six in ./.local/lib/python3.8/site-packages (from configobj>=5.0.6->mssql-cli) (1.15.0)
Requirement already satisfied: backports.csv>=1.0.0 in ./.local/lib/python3.8/site-packages (from cli-helpers<1.0.0,>=0.2.3->mssql-cli) (1.0.7)
Requirement already satisfied: terminaltables>=3.0.0 in ./.local/lib/python3.8/site-packages (from cli-helpers<1.0.0,>=0.2.3->mssql-cli) (3.1.0)
Requirement already satisfied: wcwidth in ./.local/lib/python3.8/site-packages (from prompt-toolkit<2.1.0,>=2.0.0->mssql-cli) (0.2.4)
ERROR: pgcli 3.0.0 has requirement cli-helpers[styles]>=1.2.0, but you'll have cli-helpers 0.2.3 which is incompatible.
ERROR: pgcli 3.0.0 has requirement prompt-toolkit<4.0.0,>=3.0.0, but you'll have prompt-toolkit 2.0.10 which is incompatible.
ERROR: pgcli 3.0.0 has requirement sqlparse<0.4,>=0.3.0, but you'll have sqlparse 0.2.4 which is incompatible.
Installing collected packages: cli-helpers, prompt-toolkit, sqlparse
Attempting uninstall: cli-helpers
Found existing installation: cli-helpers 2.0.1
Uninstalling cli-helpers-2.0.1:
Successfully uninstalled cli-helpers-2.0.1
Attempting uninstall: prompt-toolkit
Found existing installation: prompt-toolkit 3.0.5
Uninstalling prompt-toolkit-3.0.5:
Successfully uninstalled prompt-toolkit-3.0.5
Attempting uninstall: sqlparse
Found existing installation: sqlparse 0.3.1
Uninstalling sqlparse-0.3.1:
Successfully uninstalled sqlparse-0.3.1
Successfully installed cli-helpers-0.2.3 prompt-toolkit-2.0.10 sqlparse-0.2.4
```
**Environment**
```
> python -V
Python 3.8.2
> which python
/usr/bin/python
> pip -V
pip 20.1.1 from /home/jumpnett/.local/lib/python3.8/site-packages/pip (python 3.8)
> which pip
/usr/local/bin/pip
```