Fix all typos [skip ci]

lib/mutant/parallel.rb

@@ -1,5 +1,5 @@
 module Mutant
-  # Parallel excecution engine of arbitrary payloads
+  # Parallel execution engine of arbitrary payloads
   module Parallel
 
     # Driver for parallelized execution

lib/mutant/runner.rb

@@ -64,7 +64,7 @@ module Mutant
 
     # Return mutation test config
     #
-    # @return [Parallell::Config]
+    # @return [Parallel::Config]
     #
     # @api private
     #

spec/unit/mutant/expression_spec.rb

@@ -32,13 +32,13 @@ RSpec.describe Mutant::Expression do
 
     subject { object.try_parse(input) }
 
-    context 'on succesful parse' do
+    context 'on successful parse' do
       let(:input) { 'foo' }
 
       it { should eql(object.new(foo: 'foo')) }
     end
 
-    context 'on unsuccesful parse' do
+    context 'on unsuccessful parse' do
       let(:input) { 'bar' }
 
       it { should be(nil) }

spec/unit/mutant/parallel/worker_spec.rb

@@ -27,7 +27,7 @@ RSpec.describe Mutant::Parallel::Worker do
 
     let(:actor_names) { [:worker] }
 
-    context 'when receving :job command' do
+    context 'when receiving :job command' do
 
       before do
         expect(processor).to receive(:call).with(payload).and_return(result_payload)