State for Boost review starting 2018/09/17

This is the state of the library for the Boost review. We are integrating patches on the develop branch, while the master remains frozen. But if you want to make super sure that you see the right version, here is a tag.

v3.2

Added allocator support and simplified internals.

v3.1

Another simplification of the public interface.

• bincount() became just size()
• just use static_cast instead of axis::cast to turn the generic axis::any to the specific type
• axis objects may now have an overflow but not an underflow bin
• axis::category now stores input values that are not recognized in its new overflow bin, this acts like an "other" category

v3.0

Another major update.

• Overhaul of public interface to improve STL compatibility.
• Windows now officially supported and tested

v2.0

gcc-4.8 fix

v1.0

Legacy release