Variety of changes to documentation and example code.

1. Update version history.
2. Minor changes to the tutorial to reflect the bounds constrained
   problem.
3. Added static factory methods to the SnavelyReprojectionError.
4. Removed relative gradient tolerance from types.h as it is
   not true anymore.

Change-Id: I8de386e5278a008c84ef2d3290d2c4351417a9f1
5 files changed