Improve error message for null keys/values in getParams(). (google#203)

Fixes google#201

 Improve error message for null keys/values in getParams(). (google#203)

Fixes google#201

Update deploy credentials. (google#122)

Workaround memory leak in dispatchers. (google#119)

* Workaround memory leak in dispatchers.

Android has a long-standing known issue where local variables aren't
explicitly cleared even when they go out of scope, which can cause
their contents to leak. Since BlockingQueue#take() blocks
forever until a new item is ready, this means the last
request will remain in memory until a new request pushes it
out. Extracting a helper method is a workaround for this - see, for
example, the following CL in the Android support lib:

https://android.googlesource.com/platform/frameworks/support/+/cd07a0cfd9c9501a03c574d2d48df51c82b73e33

The following other solutions were attempted but were not sufficient:

- Clear the variable prior to take() - optimized out because the write
  is not observable, so it has no impact on the bytecode.

- Call poll() prior to take() - for some reason, this doesn't work
  when proguard optimization is on.

With code optimization, there's no guarantee that this will work, though
we now provide a Proguard config that should prevent inlining. However, it
appears to be the best we can do and follows precedent / advice from the
ART team.

Should contain no functional changes otherwise as this is just
extracting code to a helper method, and thus should be safe for 1.1.0.

Verified against provided sample app.

Fixes google#114

Bump from 1.0.1-SNAPSHOT to 1.1.0-SNAPSHOT. (google#107)

Since this release introduces new APIs to support migrating off Apache
HTTP and handling multiple headers, the minor version should be
bumped. These changes are all backwards compatible so there is no need
to bump the major version.

Volley 1.0.0 release