Removed the use of merge method as the default capabilities override custom capabilities

The use of merge method causes  default browser capabilities override custom capabilities. For example, if my target browser is `ie` and I want to run tests on `Windows 7`, typical nemo configuration would be,
```
"nemoData": {
     "targetBrowser":"ie",
     "serverCaps" : {
         "username": "sauce_username",
         "password": "sauce_password",
         "platform" : "Windows 7"
      }
}
```
However the default 'ie' capabilities has platform set to 'WINDOWS' and the use of `merge` method below overrides platform `Windows 7` to `WINDOWS` which is not desired.
`caps.merge(webdriver.Capabilities[tgtBrowser]());`