Added backup files for WinEdt

WinEdt (a popular TEX editor for windows) uses files "*.bak" for backup and "*.sav" for autosave.

TeX.gitignore

@@ -117,3 +117,7 @@ sympy-plots-for-*.tex/
 
 # xindy
 *.xdy
+
+# WinEdt
+*.bak
+*.sav