Add more tests to test_patch and test_blob

[brandonio21]

As reported in #754 , there are some strange corruption-looking things happening with creating patches. In order to find strange behavior, I've crafted the tests attached to this PR.

At the time of writing, I could only get one of the tests to reliably fail: test_patch_multi_blob

Traceback (most recent call last):
  File "/home/engshare/third-party2/pygit2/0.26.2/src/build-gcc-5-glibc-2.23/pic/test/test_patch.py", line 231, in test_patch_multi_blob
    self.assertEqual(patch_text, [patch.patch for patch in patches])
AssertionError: Lists differ: [u'diff --git a/file b/file\nd... != [u'diff --git a/file b/file\nd...

First differing element 0:
diff --git a/file b/file
deleted file mode 100644
index a520c24..0000000
--- a/file
+++ /dev/null
@@ -1,3 +0,0 @@
-hello world
-hola mundo
-bonjour le monde

diff --git a/file b/file
deleted file mode 100644
index a520c24..0000000
--- a/file
+++ /dev/null
@@ -1,3 +0,0 @@
-@^H05

Diff is 11160 characters long. Set self.maxDiff to None to see it.

I don't think this PR should be merged in until the problem is fixed.

[brandonio21]

YES! I FINALLY GOT THE BUG TO REPRO ON CI! LIFE IS GOOD!

[brandonio21]

Going to rebase this

[jdavid]

yes please

[brandonio21]

@jdavid : It's ready to be merged in! Let's do it!

[jdavid]

thanks!