BREAKING CHANGES:

• global status innodb_buffer_pool_pages have been renamed/labeled.
• innodb metrics buffer_page_io have been renamed/labeled.
• [MISC] Add Travis CI automatic testing.
• [MISC] Refactor mysqld_exporter.go into collector package.
• [FEATURE] Add mysql_up metric (PR #99)
• [FEATURE] Collect time metrics for processlist (PR #87)
• [CHANGE] Separate innodb_buffer_pool_pages status metrics (PR #101)
• [FEATURE] Added metrics from SHOW ENGINE TOKUDB STATUS (PR #103)
• [CHANGE] Add special handling of "buffer_page_io" subsystem (PR #115)
• [FEATURE] Add collector for innodb_sys_tablespaces (PR #116)