Make Index.Remove() cope with files which have been modified in the working directory

Fixes issue #95 - 2/2.

One can't GitRemove a modified file.

$ mkdir test
$ cd test
$ git init .
$ echo "a" > a.txt
$ git add .
$ git commit -m "Initial commit"

$ echo "b" >> a.txt

$ git status
no changes added to commit (use "git add" and/or "git commit -a")

$ git rm a.txt
error: 'a.txt' has local modifications
(use --cached to keep the file, or -f to force removal)

1 files changed, 1 insertions, 1 deletions

diff --git a/LibGit2Sharp/Index.cs b/LibGit2Sharp/Index.cs
index c2844385..900fc1d8 100644
--- a/LibGit2Sharp/Index.cs
+++ b/LibGit2Sharp/Index.cs
@@ -343,7 +343,7 @@ namespace LibGit2Sharp
                     throw new NotImplementedException();
                 }
 
-                if (!keyValuePair.Value.HasAny(new[] { FileStatus.Nonexistent, FileStatus.Removed, FileStatus.Untracked }))
+                if (!keyValuePair.Value.HasAny(new[] { FileStatus.Nonexistent, FileStatus.Removed, FileStatus.Modified, FileStatus.Untracked }))
                 {
                     continue;
                 }