Teensy 3.1 test code

teensy-test.ino

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal_I2C lcd(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);  // Set the LCD I2C address

void setup() {
  // set up the LCD's number of rows and columns: 
  lcd.begin(20, 4);
  // Print a message to the LCD.
  lcd.print("hello, world!");
}

void loop() {
  // set the cursor to column 0, line 1
  // (note: line 1 is the second row, since counting begins with 0):
  lcd.setCursor(0, 1);
  // print the number of seconds since reset:
  lcd.print(millis()/1000);
}

Give the following a shot:

include <LCD.h>

In any case, the library doesn't support the full teensy range of devices. Which device are you trying?