[overlay][range] Replace the explicit call to Range::erase() with version using std::copy() and traits::resize<>
[overlay] Replace *begin(rng) with front(rng)
[range] Add tests for free functions.
[range] Add erase() taking non-mutable iterators (in-line with C++11 std::vector) + tests.
[overlay] Add missing copyright info.
[overlay] Change the placement of const modifier (guidelines).
Merge pull request #64 from awulkiew/fix/erase

Replace the explicit call to Range::erase()