Updates version on README.md to 0.7.4 (holdenk#207)

Author: rgarciate

README.md

@@ -12,10 +12,10 @@ This is not my beautiful code.
 
 ## How?
 
-So you include com.holdenkarau.spark-testing-base [spark_version]_0.7.2 and extend one of the classes and write some simple tests instead.  For example to include this in a project using Spark 2.2.0:
+So you include com.holdenkarau.spark-testing-base [spark_version]_0.7.4 and extend one of the classes and write some simple tests instead.  For example to include this in a project using Spark 2.2.0:
 
 ```scala
-"com.holdenkarau" %% "spark-testing-base" % "2.2.0_0.7.2" % "test"
+"com.holdenkarau" %% "spark-testing-base" % "2.2.0_0.7.4" % "test"
 ```
 
 or
@@ -24,7 +24,7 @@ or
 <dependency>
     <groupId>com.holdenkarau</groupId>
     <artifactId>spark-testing-base_2.11</artifactId>
-    <version>${spark.version}_0.7.2</version>
+    <version>${spark.version}_0.7.4</version>
     <scope>test</scope>
 </dependency>
 ```

RELEASE_NOTES.md

@@ -4,17 +4,17 @@
  - Re-add Scala 2.10 support up to and including Spark 2.2.X series
  - Attempt to make it so that users doing SQL tests without Hive don't need the hive jars.
  - Don't reset the SparkSession provider when in reuse mode.
- - Add workaround for inaccessiable active context info in Spark 2.0
+ - Add workaround for inaccessible active context info in Spark 2.0
  - Upgrade to Hadoop 2.8.1 for mini cluster
  - Change build env after travis changes
 # 0.7.2
- - Add expiremental support to for reusing a SparkContext/Session accross multiple suites. For Spark 2.0+ only.
+ - Add experimental support to for reusing a SparkContext/Session across multiple suites. For Spark 2.0+ only.
 # 0.7.1
  - Upgrade mini cluster hadoop dependencies
  - Add support for Spark 2.2.0
  - YARNCluster now requires SPARK_HOME to be set so as to configure spark.yarn.jars (workaround for YARN bug from deprecated code in Spark 2.2).
 # 0.7
- - Add Python RDD comparisions
+ - Add Python RDD comparisons
  - Switch to JDK8 for Spark 2.1.1+
  - Add back Kafka tests
  - Make it easier to disable Hive support when running tests