Split on more characters when stripping the version metadata.

`boto3`s `metadata.json` file doesn't delimit the version specifier the way other packages I've come across seem to, so support splitting on the kinds of characters this variation might foist upon us.

Fixes: https://github.com/bazelbuild/rules_python/issues/20

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 07f84eb..d62ea20 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -107,3 +107,15 @@
 )
 
 _version_install()
+
+pip_import(
+    name = "examples_boto",
+    requirements = "//examples/boto:requirements.txt",
+)
+
+load(
+    "@examples_boto//:requirements.bzl",
+    _boto_install = "pip_install",
+)
+
+_boto_install()

examples/boto/BUILD

diff --git a/examples/boto/BUILD b/examples/boto/BUILD
new file mode 100644
index 0000000..0f22871
--- /dev/null
+++ b/examples/boto/BUILD
@@ -0,0 +1,25 @@
+# Copyright 2017 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])  # Apache 2.0
+
+load("@examples_boto//:requirements.bzl", "requirement")
+load("//python:python.bzl", "py_test")
+
+py_test(
+    name = "boto_test",
+    srcs = ["boto_test.py"],
+    deps = [requirement("boto3")],
+)

examples/boto/boto_test.py

diff --git a/examples/boto/boto_test.py b/examples/boto/boto_test.py
new file mode 100644
index 0000000..8de0e3e
--- /dev/null
+++ b/examples/boto/boto_test.py
@@ -0,0 +1,26 @@
+# Copyright 2017 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import boto3
+import unittest
+
+
+class BotoTest(unittest.TestCase):
+
+  def test_version(self):
+    self.assertEqual(boto3.__version__, '1.4.7')
+
+
+if __name__ == '__main__':
+  unittest.main()

examples/boto/requirements.txt

diff --git a/examples/boto/requirements.txt b/examples/boto/requirements.txt
new file mode 100644
index 0000000..2e58c78
--- /dev/null
+++ b/examples/boto/requirements.txt
@@ -0,0 +1 @@
+boto3==1.4.7

rules_python/whl.py

diff --git a/rules_python/whl.py b/rules_python/whl.py
index 83c4d0d..2905d77 100644
--- a/rules_python/whl.py
+++ b/rules_python/whl.py
@@ -79,7 +79,7 @@
       requires = requirement.get('requires', [])
       for entry in requires:
         # Strip off any trailing versioning data.
-        parts = entry.split(' ', 1)
+        parts = re.split('[ ><=()]', entry)
         yield parts[0]
 
   def expand(self, directory):

tools/piptool.par

diff --git a/tools/piptool.par b/tools/piptool.par
index 46da218..ba7fb26 100755
--- a/tools/piptool.par
+++ b/tools/piptool.par
Binary files differ