0.4.1 stable release

Bug fixing release. This release covers two important bugs found (issue #39 and issue #40) on BQL planner query execution.

Changelog

f1c37b4 Release 0.4.1 stable preparation
b1b92ba Remove accidentally introduced data race in data_acces.go
8138c44 Formating fix on planner_test.go
fa482d1 Fix addTriples filtering wrong logic ordering.
919e304 Fix the lexer selector between predicate and literal.
3042ad3 Typo and style fixing in documentation
dcfae60 Add description about the concurrent benchmark excecution
a9303e4 Update commandline tool documentation
eb14d31 Lint fix on function name
abb61ac Update dev version number