remove duplicate chromedriver check

[EndangeredMassa]

There were two checks for a local chromedriver. The first was not presenting the fancy error. Removing it allows the second check to do so. It will now look something like:

Preparing chrome...

/home/smassa/source/testium/lib/cli/console.js:112
      throw error;
            ^
Could not find required files for running selenium.
       - message: ENOENT, stat '/home/smassa/source/testium/bin/chromedriver'

You can provide your own version of selenium via ~/.testiumrc:

\```
[selenium]
jar = /path/to/selenium.jar
; For running tests in chrome:
chromedriver = /path/to/chromedriver
\```

testium can also download these files for you,
just execute the following before running your test suite:

$ ./node_modules/.bin/testium --download-selenium

testium will download selenium and chromedriver into this directory:
/home/smassa/source/testium/bin
Error: ENOENT, stat '/home/smassa/source/testium/bin/chromedriver'

(ignore the faux-escaped triple-`)

---

Addresses: #133

[jkrems]

LGTM

[EndangeredMassa]

published in 2.6.0