add support for 'no newline at end of file' lines

This fixes an exception when one or more of the files involved in the diff doesn't end in a new line (the hunk has to also include the last line in the file).

http://www.gnu.org/software/diffutils/manual/html_node/Incomplete-Lines.html

Example diffs:

```
--- a   2014-02-28 21:32:47.573972366 -0800
+++ b   2014-02-28 21:32:47.573972366 -0800
@@ -1 +1 @@
-test
\ No newline at end of file
+tset
\ No newline at end of file
```
```
--- a   2014-02-28 21:41:18.553861291 -0800
+++ b   2014-02-28 21:41:18.553861291 -0800
@@ -1 +1 @@
-test
\ No newline at end of file
+tset
```
```
--- a   2014-02-28 21:41:29.452561722 -0800
+++ b   2014-02-28 21:41:29.453561786 -0800
@@ -1 +1 @@
-test
+tset
\ No newline at end of file
```

These lines aren't really part of the original or modified files, but they should be part of the chunk's raw lines.