[Tests] Add more unit tests for services-core module

[RingerJK]

Have to review mapbox-java services-core module and add unit tests where required

Samples of code without unit tests:

mapbox-java/services-core/src/main/java/com/mapbox/core/utils/MapboxUtils.java

Lines 8 to 27 in 3bed27a

	public final class MapboxUtils {
	private MapboxUtils() {
	// Empty private constructor since only static methods are found inside class.
	}
	/**
	* Checks that the provided access token is not empty or null, and that it starts with
	* the right prefixes. Note that this method does not check Mapbox servers to verify that
	* it actually belongs to an account.
	*
	* @param accessToken A Mapbox access token.
	* @return true if the provided access token is valid, false otherwise.
	* @since 1.0.0
	*/
	public static boolean isAccessTokenValid(String accessToken) {
	return !TextUtils.isEmpty(accessToken) && !(!accessToken.startsWith("pk.")
	&& !accessToken.startsWith("sk.") && !accessToken.startsWith("tk."));
	}
	}

mapbox-java/services-core/src/main/java/com/mapbox/core/utils/TextUtils.java

Lines 82 to 88 in 3bed27a

	public static String formatCoordinate(double coordinate, int precision) {
	String pattern = "0." + new String(new char[precision]).replace("\0", "0");
	DecimalFormat df = (DecimalFormat) DecimalFormat.getInstance(Locale.US);
	df.applyPattern(pattern);
	df.setRoundingMode(RoundingMode.FLOOR);
	return df.format(coordinate);
	}