Create MicrosoftOffice

Continuation of https://github.com/github/gitignore/pull/594/ and details from http://support.microsoft.com/kb/211632

Global/MicrosoftOffice.gitignore

+*.tmp
+
+# Word temporary
+~$*.doc*
+
+# Excel temporary
+~$*.xls*
+
+# Excel Backup File
+*.xlk