Document the 'B' type and the difference between 'b' & 'B'. Addresses part of issue https://github.com/vitaut/format/issues/5

Document that "#x" adds prefix "0x" and "#X" adds "0X". Addresses part of issue https://github.com/vitaut/format/issues/5

add support for older GCC versions

Always use noexcept for gcc >= 4.8 because dtors are implicitly noexcept there. Remove binu and 'B' specifier.

Added support for binary modifier

Disallow writing a wide string to a char stream and vice versa, because there is no good way to implement these function without knowing the encodings and what std::ostream doesn't make any sense.