* add yamllint command to travis CI

installs and runs a linter across the YAML in the
project to ensure consistency in the written YAML.

this uses yamllint and the default yamllint config with
"truthy" and "line-length" disabled.

* run dos2unix on CRLF files

* YAMLLINT: remove trailing spaces

* YAMLLint: add YAML document start

* YAMLLint: too many spaces around bracket

* YAMLLint: fix indentation

* YAMLLint: remove duplicate key

* YAMLLint: newline at end of file

* YAMLLint: Too few spaces after comma

* YAMLLint: too many spaces after colon