Bug 1098406: Fix gaia repository path.

A commit in the mozilla-central repository [1] broke the gaia URL
repository URL construction code.

We now make sure our code works independent of the leading slash
presence.

[1] http://hg.mozilla.org/mozilla-central/rev/f3782f5c2710
Bug 1104007 - Add mochitest and mochitest-media tasks for b2g emulator r=lightsofapollo
Merge pull request #38 from walac/bugz/1098406

Bug 1098406: Fix gaia repository path.
Bug 1102085: Use "mach environment" to extract the object directory.

If "topobjdir" is None, use default object directory.
Merge pull request #41 from walac/bugz/1102085

Bug 1102085: Use "mach environment" to extract the object directory.
Merge pull request #40 from gregarndt/b2g_emulator_mochitest

Bug 1104007 - add mochitests task for b2g emulator r=lightsofapollo
Bug 1099259 - added tasks for mn and mnw tests on emulator
r=lightsofapollo