Add option to avoid removing repeated replacement

[rocktimsaikia]

Feature of avoid removing repeated replacement added suggested by the issue #10.

A new option is now available named 'condenseReplacements' as suggested by @sindresorhus on issue #10

filenamify('/path/to/file---name.ext"', {replacement: '-', condenseReplacements: true});
// => path-to-file---name.ext

Test case added along with updated README

// @sindresorhus

Fixes #10

[sindresorhus]

The default value should be true, to preserve existing behavior.

[sindresorhus]

This sentence is inconsistent compared to the other ones. And it's also incorrect. It doesn't describe what the option does, but rather what it doesn't do.

[rocktimsaikia]

The default value should be true, to preserve existing behavior.

@sindresorhus Ah, I see. This would be a breaking change then! That's why I hesitated to set it true by default.

[papb]

@rocktimsaikia No; the default value being true is exactly what makes it not a breaking change.

[sindresorhus]

Bump