Fixed version checking for reportlab to work with newer versions.

While requirements.txt would always install the newest version of
reportlab this code would only allow versions of reportlab that
started with "2" (so 3.0 would be rejected).
This has now been fixed to allow any version of reportlab from
2.1 onwards.

I found this quite elegant use of map to turn the version into a
turple at the link below:
https://github.com/chrisglass/xhtml2pdf/commit/52d9704d1d9a7d529cc2f9064c0677a1641641e2