v0.3.0

Fixes:

• fixed some pedantic clang warnings
• fixed some minor documentation errors

Additions:

• added node::value() and node::value_or()
• added node_view::value()
• added relops for the date/time classes
• added TOML_ALL_INLINE and TOML_IMPLEMENTATION options
• added preliminary support for ICC

Removals and Deprecations:

• removed <cmath> dependency