fix annuity computation
fixed case r=0.0
improve check for r=0
Switch to absolute paths for styles and menu links.

This allows the menu to work also in pages not in the base directory.
Add missing style file to a few pages.
Remove unqualified calls to make_shared.

On VC++12, argument-dependent lookup was causing ambiguities
between boost::make_shared and std::make_shared when vectors
were passed among the arguments.

Thanks to Armel Wambou for the heads-up.
fixed theta issue for some american fdm engines. Theta should be
measured after the early exercise condition gets applied.
fix interpolation of option dates when evaluation date changes (thanks to Shen Hui)
Merge pull request #62.
Merge pull request #69.
Merge pull request #71.
Merge remote-tracking branch: upstream/master