fix(semver): range handling includes prerelease when it should not

A bug in the semver package caused prereleases to be included in
version ranges by default. Prereleases, per the spec, are not
expected to be API compatible with the releases themselves.

The semver package now ignores prereleases when evaluating
constraints when the constraint does not contain a prerelease. If
the constraint contains a prerelease they are evaluated.

glide.lock

@@ -1,5 +1,5 @@
-hash: 99054419731f37edfc9fca9ae35d473635e865f1e1c9a7633ec36963dfa25c2a
-updated: 2016-11-22T16:38:51.234855217-08:00
+hash: 89695daf5f2de706b79fdd8e8b095f9514f418c0fbcf80d7fdca4c208d114d19
+updated: 2016-11-29T11:37:40.998261206-05:00
 imports:
 - name: cloud.google.com/go
   version: 3b1ae45394a234c385be014e9a488f2bb6eef821
@@ -199,7 +199,7 @@ imports:
 - name: github.com/juju/ratelimit
   version: 77ed1c8a01217656d2080ad51981f6e99adaa177
 - name: github.com/Masterminds/semver
-  version: 808ed7761c233af2de3f9729a041d68c62527f3a
+  version: 52edfc04e184ecf0962489d167b511b27aeebd61
 - name: github.com/Masterminds/sprig
   version: 8f797f5b23118d8fe846c4296b0ad55044201b14
 - name: github.com/mattn/go-runewidth

glide.yaml

@@ -9,7 +9,7 @@ import:
   version: ^2.6
 - package: github.com/ghodss/yaml
 - package: github.com/Masterminds/semver
-  version: 1.1.0
+  version: ~1.2.1
 - package: github.com/technosophos/moniker
 - package: github.com/golang/protobuf
   version: df1d3ca07d2d07bba352d5b73c4313b4e2a6203e