The parse function should not be imported by itself. Types were updated accordingly.

Description

The parse function should not be imported by itself, as explained in issue#45. The issue arises because the types allow the parse function to be imported by itself, as a named export.
I changed the types so that the only possible import is the default export, like
import ErrorStackParser from 'error-stack-parser';
and the parse function can only be used like
ErrorStackParser.parse(error)

Motivation and Context

This PR updates the types so that Issue #45 cannot occur, because the parse function cannot be imported by itself.

How Has This Been Tested?

I tested the new types in a repo where I use error-stack-parser.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• node_modules/.bin/jscs -c .jscsrc error-stack-parser.js passes without errors
• npm test passes without errors
• I have read the contribution guidelines
• I have updated the documentation accordingly
• I have added tests to cover my changes