Remove invalid company session setter

[thewheat]

Why?

• Addresses this issue CompanyUpdateBuilder.java contains function to update session_count, which isn't possible #231
• Looks like when updating a company or updating a user (after adding a company to the user), we are setting company session value
• Company session is not something modifiable via the API and returns a Exception in thread "main" io.intercom.api.ClientException: bad 'session_count' parameter error

How?

• Remove references to setSessionCount for companies

Test Code that will fail on current code base but will succeed with these new changes

        HashMap<String, String> map = Maps.newHashMap();
        map.put("company_id", "1");
        Company company = Company.find(map);
        company.setName("Blue Sun Corporation");
        Company.update(company);

        map = Maps.newHashMap();
        map.put("user_id", "1");
        User user = User.find(map);
        user.addCompany(company);
        User.update(user);