Add option to use a custom yaml mapping file

Adds an optional mapping-file switch to TestFileFinder executable.

Usage: tff [options] [...file_paths]
    -f, --mapping-file FILE          Use a custom test mapping file

The mapping-file is a yaml file containing to entries to match file patterns to its test files. The patterns may include capturing groups to be used to identify the test file. For example:

mapping:
  # maps `app/file.rb` to `spec/file_spec.rb`
  - source: app/(.+)\.rb
    test: spec/%s_spec.rb
  # maps `db/schema.rb` to `spec/db/schema_spec.rb`
  - source: db/schema.rb
    test: spec/db/schema_spec.rb
  # maps `ee/app/models/ee/user.rb` to `ee/spec/models/user_spec.rb`
  - source: ee/app/(.*/)ee/(.+)\.rb
    test: ee/spec/%s%s_spec.rb

Example usage:

$ tff -f tests.yml lib/test_file_finder/mapping.rb lib/test_file_finder/option_parser.rb | xargs bundle exec rspec

TestFileFinder::Mapping
  .load
    loads test_map file into a Mapping
    with incorrect yaml
      raises error
    with incomplete mapping
      rejects with error
  #map
    adds source file regex pattern and test file matcher to pattern matchers
    when given a string pattern
      adds string pattern to pattern matchers
  #match
    returns matching test file names
    with multiple matching test files
      returns all matching test file names
    when the file does not match given pattern
      returns nothing
    with multiple matching mappings
      returns all matching test file names
    with matching subdirectory
      returns nothing
  #|
    merges mapping with another mapping
    with a repeated pattern
      merges both matchers for the same pattern

TestFileFinder::OptionParser
  --mapping-file FILE
    is expected to eq "mapping.yml"
  -f FILE
    is expected to eq "mapping.yml"

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14 examples, 0 failures

Closes #8 (closed)