sequence_from_blastdb: raise TypeError if the argument's type is unexpected
sequence_from_blastdb: raise TypeError if the argument's type is unexpected

We threw ArgumentError which is logically wrong. I found a related discussion
on Ruby's issue tracker regarding this; see [1].

[1]: http://redmine.ruby-lang.org/issues/2830

Signed-off-by: Anurag Priyam <6e6ab5ea9cb59fe7c35d2a1fc74443577eb60635@gmail.com>

jasminZ/sequenceserver,vivekiitkgp/sequenceserver,deepakunni3/sequenceserver,deepakunni3/sequenceserver,aldermossy/sequenceserver,IsmailM/sequenceserver,jasminZ/sequenceserver,elsiklab/sequenceserver,yeban/sequenceserver,aldermossy/sequenceserver,lepbase/lepbase-sequenceserver,elsiklab/sequenceserver,vivekiitkgp/sequenceserver,IsmailM/sequenceserver,IsmailM/sequenceserver,lepbase/lepbase-sequenceserver,aldermossy/sequenceserver,lepbase/lepbase-sequenceserver,yeban/sequenceserver,deepakunni3/sequenceserver,jasminZ/sequenceserver,elsiklab/sequenceserver,yeban/sequenceserver,yeban/sequenceserver,vivekiitkgp/sequenceserver,aldermossy/sequenceserver