Added cheatsheets for markdown, ncat, and sqlmap.

Some cheatsheets that I created for a project for CIS4930, Ethical
Hacking and Penetration Testing. On request of the professor, I will be
sending a pull request with these cheatsheets.

cheatsheets/markdown

@@ -0,0 +1,41 @@
+# headers
+h1 header
+=========
+h2 header
+---------
+
+# blockquotes
+> first level and paragraph
+>> second level and first paragraph
+>
+> first level and second paragraph
+
+# lists
+## unordered - use *, +, or -
+        * Red
+        * Green
+        * Blue
+
+## ordered
+        1. First
+        2. Second
+        3. Third
+
+# code - use 4 spaces/1 tab
+regular text
+        code code code
+or:
+Use the `printf()` function
+
+# hr's - three or more of the following
+***
+---
+___
+
+# links
+This is [an example](http://example.com "Title") inline link.
+
+# emphasis
+*em* _em_
+
+**strong** __strong__