Fix snpEff version detection (issue #165)

Recent SnpEff versions don't have the "SnpEff" name in the version
information anymore, which breaks loading (maj_version will become None)

This patch fixes the issue by:

- cleaning the string up (no more nested quotes)
- splitting the string
- checking if the first token includes "SnpEff"
Merge pull request #166 from cswegger/fix-snpeff-version

Fix snpEff version detection (issue #165)