minor tweaks in GLM2:
 a) fixed cross validation in lambda_search (was only storing the last model's xval)
 b) fixed display of lambda on glmview page  (refactoring turned &lambda; into &lambda_value; in html output)
 c) updated defaults for nlambda and lambda_min params in R interface to -1 (so that h2o will decide based on the data)
 d) added max_predictors param to R interface.
Merge branch 'master' of github.com:0xdata/h2o