Update check-procs plugin.

- Convert `read_pid` class method to instance method and use it inside
  `#run` instead of call it during the parsing of options. There was a
  "stack level" too deep" with the old way if you specify an unexisting
  pidfile path.

  Ex:
  ```
  ruby check-procs.rb -f unknown_file.unknown_ext
Check failed to run: stack level too deep, ["/var/lib/gems/1.9.1/gems/mixlib-cli-1.4.0/lib/mixlib/cli.rb:162"]
/var/lib/gems/1.9.1/gems/sensu-plugin-0.2.2/lib/sensu-plugin/cli.rb:63:in `block in <class:CLI>': undefined method `warning' for nil:NilClass (NoMethodError)
  ```

- Update `read_pid` method to check if file with pid exists instead of
  rescue the exception directly.

  Exception flow is not a good practice and the performance is very poor.
  There is an example in: https://gist.github.com/areina/9233841
Fix rubocop offence in check-procs plugin.
Improve some details in check-procs plugin.

- Update .read_pid(). Use .strip() method instead of .chomp().
- Remove outer `()` in conditional statement.
noauto option mountpoints should be ignored

Mount Points with the noauto option specified are not expected to be mounted, and not mounted by the system at boot time. They are mostly temporarily mounted when needed, listed in /etc/fstab only for convenience, and highly unlikely to be serving critical data on server systems.
Merge pull request #499 from areina/master

Update check-procs plugin.
Merge pull request #504 from new23d/patch-1

noauto option mountpoints should be ignored