change mechanize dependency version

When i am running 
```shell
bundle install 
```
in my rails app, i have the following:
```shell
Bundler could not find compatible versions for gem "mime-types":
  In Gemfile:
    vk-ruby (>= 0) ruby depends on
      mechanize (>= 2.7.3, ~> 2.7) ruby depends on
        mime-types (~> 2.0) ruby

    rest-client (>= 0) ruby depends on
      mime-types (1.25.1)
```
So, it seems there a lot of gems ( mail, rest-client) which depends on old version of mime-types.
Mime-types used by mechanize, so i wish it will be merged and you will not restrict it by [patch version](http://semver.org/) , only by minor version.