Make releasedata.Product usable in 'with' expression (#294)

This way the writing of the JSON file is handled automatically if the update does not fail.
It pave the way to further global improvements, such as a better error handling.

src/oracle-jdk.py

@@ -5,19 +5,18 @@ from requests_html import HTMLSession
 
 This script is using requests-html because the page needs JavaScript to render correctly."""
 
-product = releasedata.Product("oracle-jdk")
-r = HTMLSession().get('https://www.java.com/releases/')
-r.html.render(sleep=1, scrolldown=3)
+with releasedata.ProductData("oracle-jdk") as product_data:
+    r = HTMLSession().get('https://www.java.com/releases/')
+    r.html.render(sleep=1, scrolldown=3)
 
-previous_date = None
-for row in r.html.find('#released tr'):
-    version_cell = row.find('td.anchor', first=True)
-    if version_cell:
-        version = version_cell.attrs['id']
-        date_str = row.find('td')[1].text
-        date = dates.parse_date(date_str) if date_str else previous_date
-        product.declare_version(version, date)
-        previous_date = date
+    previous_date = None
+    for row in r.html.find('#released tr'):
+        version_cell = row.find('td.anchor', first=True)
+        if version_cell:
+            version = version_cell.attrs['id']
+            date_str = row.find('td')[1].text
+            date = dates.parse_date(date_str) if date_str else previous_date
+            product_data.declare_version(version, date)
+            previous_date = date
 
-product.remove_version('1.0_alpha')  # the only version we don't want, a regex is not needed
-product.write()
+    product_data.remove_version('1.0_alpha')  # the only version we don't want, a regex is not needed