Rename job 'type' property -> 'job_type'.

Addresses:
#1469 (comment)

docs/bigquery-usage.rst

@@ -279,7 +279,7 @@ List jobs for a project:
    >>> from gcloud import bigquery
    >>> client = bigquery.Client()
    >>> jobs, token = client.list_jobs()  # API request
-   >>> [(job.name, job.type, job.created, job.state) for job in jobs]
+   >>> [(job.name, job.job_type, job.created, job.state) for job in jobs]
    ['load-table-job', 'load', (datetime.datetime(2015, 7, 23, 9, 30, 20, 268260, tzinfo=<UTC>), 'done')]
 
 Querying data (synchronous)
@@ -333,7 +333,7 @@ Background a query, loading the results into a table:
    >>> job.write_disposition= 'truncate'
    >>> job.name
    'fullname-age-query-job'
-   >>> job.type
+   >>> job.job_type
    'query'
    >>> job.created
    None
@@ -414,7 +414,7 @@ the job locally:
    >>> job.write_disposition = 'truncate'
    >>> job.name
    'load-from-storage-job'
-   >>> job.type
+   >>> job.job_type
    'load'
    >>> job.created
    None
@@ -471,7 +471,7 @@ located on Google Cloud Storage.  First, create the job locally:
    ... job.write_disposition = 'truncate'
    >>> job.name
    'extract-person-ages-job'
-   >>> job.type
+   >>> job.job_type
    'extract'
    >>> job.created
    None
@@ -525,7 +525,7 @@ First, create the job locally:
    ...     'copy-table-job', destination_table, source_table)
    >>> job.name
    'copy-table-job'
-   >>> job.type
+   >>> job.job_type
    'copy'
    >>> job.created
    None

gcloud/bigquery/job.py

@@ -129,7 +129,7 @@ def __init__(self, name, client):
         self.name = name
 
     @property
-    def type(self):
+    def job_type(self):
         """Type of job
 
         :rtype: string

gcloud/bigquery/test_job.py

@@ -235,7 +235,7 @@ def test_ctor(self):
         self.assertTrue(job.destination is table)
         self.assertEqual(list(job.source_uris), [self.SOURCE1])
         self.assertTrue(job._client is client)
-        self.assertEqual(job.type, self.JOB_TYPE)
+        self.assertEqual(job.job_type, self.JOB_TYPE)
         self.assertEqual(
             job.path,
             '/projects/%s/jobs/%s' % (self.PROJECT, self.JOB_NAME))
@@ -689,7 +689,7 @@ def test_ctor(self):
         self.assertTrue(job.destination is destination)
         self.assertEqual(job.sources, [source])
         self.assertTrue(job._client is client)
-        self.assertEqual(job.type, self.JOB_TYPE)
+        self.assertEqual(job.job_type, self.JOB_TYPE)
         self.assertEqual(
             job.path,
             '/projects/%s/jobs/%s' % (self.PROJECT, self.JOB_NAME))
@@ -988,7 +988,7 @@ def test_ctor(self):
         self.assertEqual(job.source, source)
         self.assertEqual(job.destination_uris, [self.DESTINATION_URI])
         self.assertTrue(job._client is client)
-        self.assertEqual(job.type, self.JOB_TYPE)
+        self.assertEqual(job.job_type, self.JOB_TYPE)
         self.assertEqual(
             job.path,
             '/projects/%s/jobs/%s' % (self.PROJECT, self.JOB_NAME))
@@ -1296,7 +1296,7 @@ def test_ctor(self):
         job = self._makeOne(self.JOB_NAME, self.QUERY, client)
         self.assertEqual(job.query, self.QUERY)
         self.assertTrue(job._client is client)
-        self.assertEqual(job.type, self.JOB_TYPE)
+        self.assertEqual(job.job_type, self.JOB_TYPE)
         self.assertEqual(
             job.path,
             '/projects/%s/jobs/%s' % (self.PROJECT, self.JOB_NAME))