simple checks for whether we have enough eigenvectors
added test for changing n_components in tICA
missed a bracket.
in tICA._solve added check for whether we've actually run fit on some data yet.
tests for tica pass
bugfix self.n_observations -> self.n_observations_
Merge pull request #306 from schwancr/tica_n_components_fix

simple checks for whether we have enough eigenvectors