Charts not created correctly when worksheet should be quoted
*Created originally on Bitbucket by [jpaduart (Johan Paduart)](https://bitbucket.org/%7Bb01ebd5d-4d77-4709-abff-cc2df7f0be34%7D/)*
When running the code below, the chart reference to the worksheet with a "%" in the sheet name, does not appear.
Similar to
https://bitbucket.org/openpyxl/openpyxl/issues/788
(sheet reference should be quoted)
```
#!python
import openpyxl
from openpyxl.chart import LineChart, Reference, Series
wb = openpyxl.Workbook()
ws1 = wb.create_sheet("SheetWith%", 0)
ws2 = wb.create_sheet("SheetWithout", 0)
ws3 = wb.create_sheet("Graph")
lc = LineChart()
data = Reference(ws1, min_col = 1, min_row = 24, max_col = 1, max_row = 64)
series = Series(data, title = "With%")
lc.append(series)
data = Reference(ws2, min_col = 1, min_row = 24, max_col = 1, max_row = 64)
series = Series(data, title = "Without%")
lc.append(series)
ws3.add_chart(lc, "A1")
wb.save('test.xlsx')
```
issue