On Tuesday, Uber Technologies Inc will, for the first time, allow drivers to collect tips through the Uber smartphone app. The company said that this was part of a broader effort to improve its often controversial relationship with its drivers. Uber has for years opposed adding a tipping feature to the app, which upset drivers who have argued that tips would help compensate for decreasing wages. Beginning on Tuesday, drivers in Houston, Minneapolis and Seattle can collect tips. Uber said that the feature will be available to all drivers by the end of July.