Check for ENOENT and EISDIR errors. Fixes gh-7

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Always use latest version of polyfills

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Update to latest Object.assign semantics

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
servoWrite should have it's own Pin object behavior

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Fixes servo period/duty cycles

Initial support for PWM contained 3 mistakes:
1. Aliasing servoWrite to analogWrite (I made this same mistake in Spark-IO… lesson learned yet?) this can't be done because analogWrite accepts 8-bit values 0-255. servoWrite accepts a value that represents "degrees" 0-180
2. Because I was aliasing, the "degree" value was being scaled as though it was 0-255
3. Basic PWM can be from 0-P where P is the period in nanoseconds. P was set to 2400000ns. Servo PWM functions in a range from ~500000ns to ~2300000ns*.

Note: The given servo range has been tested with the following servos:

- Hi-Tec HS-55
- Hi-Tec HS-311
- Hi-Tec HS-322HB
- Hi-Tec HS-485HB
- Hi-Tec HS-422
- Hi-Tec HS-645MG
- Hi-Tec HS-755HB
- Hi-Tec HS-805BB
- Hi-Tec HS-5685MH
- Hi-Tec HSR-1425CR
- EMAX ES08A11 II
- Futuba S3003
- Tower Pro MG995
- Power HD 1501MG

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
v0.1.0

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Update .npmignore

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
Adds new example: servo-write.js

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>
v0.1.1

Signed-off-by: Rick Waldron <waldron.rick@gmail.com>