Add nil guard to Syntax.conversion_target_node?
Support basic conversion of have(x).items matcher

This is related to #5.

TODO:
* Runtime information is not considered.
* Whether subject responds to query methods (#size, #count and #length)
  is not considered.
* Expectation on collection owner is not considered.
  e.g. team.should have(9).players
Use terminal effects in help text
Rename --commit-message option to --generate-commit-message
Refactor Syntax.conversion_target_node? with Mixin::Send
Fix inappropriate caching in spec
Redesign dynamic analysis logic
Rename Syntax.conversion_target_node? to .target_node?
Dump rspec output when failed even if silent mode in DynamicAnalyzer
Support conversion of have(x).items matcher with collection owner

This is related to #5.
Use keyword arguments in DynamicAnalyzer.new
Rewrite and run rspec only against specified paths in DynamicAnalyzer
Consider available size query methods in conversion of have(x).items

This closes #5.
Wrap here document with helper method properly in dynamic analysis