Move all floats to doubles

The code was developed initially around a pid loop implemented using
floats.  Therefore, the code was converting back and forth between
double for sensor values as inputs and outputs from this PID loop.

Change-Id: I2d2919e1165103040729c9f16bb84fde3dd6b81b
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/pid_fancontroller_unittest.cpp b/test/pid_fancontroller_unittest.cpp
index 57932c9..ad646bf 100644
--- a/test/pid_fancontroller_unittest.cpp
+++ b/test/pid_fancontroller_unittest.cpp
@@ -234,9 +234,9 @@
     // Grab pointer for mocking.
     SensorMock* sm1 = reinterpret_cast<SensorMock*>(s1.get());
 
-    // Converting from float to double for expectation.
-    float percent = 80;
-    double value = static_cast<double>(percent / 100);
+    // Converting from double to double for expectation.
+    double percent = 80;
+    double value = percent / 100;
 
     EXPECT_CALL(z, getSensor(StrEq("fan0"))).WillOnce(Return(s1.get()));
     EXPECT_CALL(*sm1, write(value));