ruby: in Eigen, provide a default argument for tolerance in approx?
ruby: remove a copy/pasted test from where it does not belong
spline: fix Spline#dup

initialize_copy became private on ruby 2.0 or 2.1. This is backward
compatible with 1.9
ruby: in eigen-related tests, use approx? instead of a self-made test on the norm
ruby: fix Eigen::Vector3.assign=
Merge pull request #1 from rock-core/bugfix_ruby_vector3_assign

ruby: fix Eigen::Vector3.assign=
test: depend on minitest only

There's a collision between ruby's built-in minitest library and the
gem (they are incompatible), which breaks testrb and testing in general.

Switch to using only minitest