Fixed bug in 'oe' script when passing no arguments

When no arguments passed to 'oe' script next exception was thrown:

```
Traceback (most recent call last):
  File "./oe", line 5, in <module>
    if sys.argv[1] == 'run-tests':
IndexError: list index out of range
```
Merge pull request #51 from katyukha/oe-fix-1

Fixed bug in 'oe' script when passing no arguments