Refactor RSpec's code

[sachin21]

describe '.usage' do
  it 'returns String class' do
    expect(Space2underscore.usage).to be_a(String)
  end

  it 'does not return an blank string does' do
    expect(Space2underscore.usage).not_to be_nil
  end
end

does not return a blank string does

This test is needless because the above example was completely satisfied the specification.