(#35) Add --pager option for diff.interactiveFilter

[ghost]

Fix #35

This PR changes below.

• If user supplies --pager option, dfs won't custom meta lines.

Usecase

[interactive]
	diffFilter = diff-so-fancy --pager

Motivation

I'm a contributor of git-delta and solved the same problem. I found #35 issue today and did a same approach.

Remarks

I'd like to add a test. In order to test, we need to confirm each outputs below have same line-number.

# for input
git diff-files -p --no-color

# for output
git diff-files -p --color | diff-so-fancy --pager

However, I'm not familiar with bats, and bats seems not to able to achieve .... Is there any good suggestion to add a test? (With the hardest way, we need to prepare diff outputs text file.)

[ghost]

Sorry, I didn't notice somebody had already created same PR 14 hours ago.
I'm gonna close this.