You can find a link to the Bosch BME280 sensor datasheet on Adafruit's BME280 breakout product web page, under "documents". Table 35 and Figure 17 of the datasheet provide complete I2C connection guidance.
I ordered the I2C version board that includes a 5V regulator and level shifter from eBay seller in China. What was delivered instead, was a 3.3V version (no on-board voltage regulator or shifter). This 3.3v board does work well on a 3.3v Arduino. The board tested good on both I2C and SPI connections using Adafruit's BME280 library.
Since the board is configured for I2C hex address 0x76, Adafruit's example sketch "bme280test.ino" needs to be modified as follows: Change in setup(), line: bme.begin();, change to: bme.begin(0x76);.
The breakout board I have has 10K pullup resistors, where as the datasheet recommends 4.7K pullups. The board also has a 10K resistor pulling SDO to GND, so according to the datasheet, I2C address is set to hex address 0x76.