This would be a crime against literature. Twain scholar Steven Railton of The University of Virginia is quoted as calling this "a terrible idea." According to the article,
The language depicts America's past, Railton said, and the revised book was not being true to the period in which Twain was writing. Railton has an unaltered version of 'Huck Finn' coming out later this year that includes context for schools to explore racism and slavery in the book. 'If we can't do that in the classroom, we can't do that anywhere,' he said.As one might expect, a quotation from Twain himself says it best. Back to the AP: "Twain was particular about his words. His letter in 1888 about the right word and the almost right one was 'the difference between the lightning bug and the lightning.'"
Censoring the word "nigger" from Mark Twain's books robs our culture of the knowledge of a part of the word's historical context. How can students understand the meaning and impact this word has had if we pretend it never existed? In every work Mark Twain published he worked to use "just the right word". We don't get to change them.