Fix test package name in test_suite.py

Before this, the name for the export related tests was missing causing those tests to be skipped on the Travis CI builds.
Increase upper bound on size in excel export tests

Given this constraint in setup.py -- 'openpyxl>=1.6,<1.7' -- openpyxl 1.6.2 is getting installed during Travis CI builds. This version returns content slightly larger(4 bytes) than the previous upper bound. I increased the upper bound 10 bytes to account for variability in openpyxl versions.