improve execute many

[maxbachmann]

execute many can handle different types now aswell and not only tuples.
This way it does not require the user to create a tuple to bind a single value:

execute_many(db, "INSERT INTO test VALUES (?, ?)",
            1,
            std::make_tuple(2),
            std::make_tuple(3, "three")
        );

currently this means it supports tuples and single values when only one value has to be bound, since these are the only types supported by VariadicBind right now

[coveralls]

Coverage remained the same at 96.502% when pulling d292c6d on maxbachmann:master into a637d24 on SRombauts:master.

[maxbachmann]

fixed #206

[maxbachmann]

@SRombauts it's fixed now. However we should think about changing the name of the bind function to something like sql_bind so it is no name of a standard function anymore in the next major release

[SRombauts]

Yes please, if you can work on this, it would be nice to improve the naming before I release a new version.

[maxbachmann]

You could open a 3.x branch

[SRombauts]

Thanks, I have integrated your fix!

[SRombauts]

Regarding a 3.x branch, I am not yet ready to dedicated enough time on this