simplify design

[septs]

Convenient preset rules

gitignore.Combine(
    gitignore.FromLines(".", []string{".DS_Store", "License.nfo"}),
    gitignore.FromLines("./foo", []string{"*.dng"}),
    gitignore.FromLines("./foo/bar", []string{"*.log"}),
    // ... user ignore patterns ...
)

closes #10

[septs]

I think the method name can be shortened:

Original method name	New method name	Actual use
NewGitIgnore	FromFile	gitignore.FromFile
NewGitIgnoreFromReader	FromReader	gitignore.FromReader
NewGitIgnoreFromLines	FromLines	gitignore.FromLines

[septs]

New feature:

gitignore.NewFromFile("to/your/.ignore", "to", "your")
// eq
gitignore.NewFromFile("to/your/.ignore", filepath.Join("to", "your"))

[septs]

@monochromegane

[monochromegane]

Thank you for your suggestion.
But I have no plans to change the interface so far.