First, you won't need
#include <application.h>
#include <spark_wiring_i2c.h>
If you are working with an .ino file application.h (or better the newer Particle.h) is included automatically and that in turn will include the headers needed to use Wire in your code.
Next, the address.
You were using another board with exactly the same address in this thread
The hardware (8bit) base address of the device is 0xC0 but for Wire you need the 7bit address (0xC0 >> 1 or 0b11000000 >> 1 which is 0b01100000 or 0x60).
So you might have an address collision unless you set the address of the PCA9531 board to something else.
For that board 0x60 being the 7-bit-base address the bottom three bits are settable via the A0~A2 pins on the LED driver shield via the address jumpers.
But most importantly on the hardware side, you'll need to have pull-up resistors on your I2C lines. The Adafruit MPL3115A2 board has already got 10k in place. But if you are using it in conjunction with the CE board where you can apply them via the dedicated jumpers on your board if you are not using the CE master board you need to make sure the over all pull-up value is still OK.
And once you have the HW set up correctly, you can move on to the SW side of things.
And for reading the MPL3115A2, you'll need to do the reading in loop() and not only once in setup().