Add Rfc time class and bump version

pom.xml

@@ -7,7 +7,7 @@
   <modelVersion>4.0.0</modelVersion>
   <groupId>com.github.trickl</groupId>
   <artifactId>model-oanda</artifactId>
-  <version>0.1.7-SNAPSHOT</version>
+  <version>0.1.8-SNAPSHOT</version>
   <packaging>jar</packaging>
   <developers>
     <developer>

src/main/java/com/trickl/text/oanda/Rfc3339.java

@@ -0,0 +1,22 @@
+package com.trickl.text.oanda;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+
+public class Rfc3339 {
+
+  public static final String WITH_NANO_PRECISION = "yyyy-MM-dd'T'HH:mm:ss.nnnnnnnnnX";
+  public static final String WITH_MILLISECOND_PRECISION = "yyyy-MM-dd'T'HH:mm:ss.nnnX";
+  public static final String WITH_SECOND_PRECISION = "yyyy-MM-dd'T'HH:mm:ssX";
+  public static final DateTimeFormatter YMDHMSN_FORMATTER =
+      DateTimeFormatter.ofPattern(WITH_NANO_PRECISION).withZone(ZoneId.of("UTC"));
+  public static final DateTimeFormatter YMDHMS_FORMATTER =
+      DateTimeFormatter.ofPattern(WITH_SECOND_PRECISION).withZone(ZoneId.of("UTC"));
+  public static final Instant YEAR_OF_2264 = Instant.ofEpochMilli(9223368436000L);
+  public static final DateTimeFormatter YMDHMSM_FORMATTER =
+      DateTimeFormatter.ofPattern(WITH_MILLISECOND_PRECISION).withZone(ZoneId.of("UTC"));
+  public static final Instant YEAR_OF_1970 = Instant.ofEpochMilli(1);
+
+  private Rfc3339() {}
+}