add missing requirements.txt

Author: chfw

docs/requirements.txt

@@ -0,0 +1,7 @@
+https://github.com/chfw/lml/archive/master.zip
+https://github.com/pyexcel/pyexcel/archive/master.zip
+https://github.com/pyexcel/pyexcel-io/archive/v0.4.x.zip
+https://github.com/pyexcel/pyexcel-xls/archive/v0.4.x.zip
+https://github.com/pyexcel/pyexcel-handsontable/archive/master.zip
+https://github.com/pyexcel/sphinxcontrib-excel/archive/master.zip
+