Resolve shell env inheritance issue

[connectdotz]

When vscode failed to initialize the process env correctly (only for non-windows platforms), users might see errors during jest run like

env: node: No such file or directory

This PR adds the ability to execute jest commandLine through a spanwed login shell to avoid dependency on vscode env initialization. By default, we will still be spawning jest process via non-login/non-interactive shell, as it is more efficient. The login-shell execution is a opt-in option right now. Possible future enhancement, if desired, is to utilize the vscode terminal.integrated.profiles option to automatically use the same shell as the vscode terminal.

• expand jest.shell to allow LoginShell for non-windows platform, see support spawn process in a login-shell for non-windows platform jest-editor-support#87 for details
• update README
• bump package dependency and version

fix #865
fix #867
fix #845
fix #828
fix #833

[coveralls]

Pull Request Test Coverage Report for Build 2416857126

• 27 of 27 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 95.39%

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Totals
Change from base Build 2388284105:	0.02%
Covered Lines:	2593
Relevant Lines:	2664

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💛 - Coveralls