mirroring calabash-ios console command

* introduced a CALABASH_IRBRC variable

1. set IRBRC to CALABASH_IRBRC if it exists
2. if ./.irbrc is present, set IRBRC to this local .irbrc
3. otherwise IRBRC is et to the calabash-android gem irbrc file

* launching irb with ruby `exec` rather than starting with a system
  call.  This is preferrable because `exec` swaps out the current
  process with `irb` rather than running `irb` in the context of
  current process.
using single quotes vs. double quotes (style change)
console cmd prints the path the to the irb init file
Initial generic multi touch gesture commit.
Added basic gestures 'tap', 'double_tap', 'long_press', 'swipe', 'fling' and 'pinch'
Fixed a bug in webview coordinate scaling
Fixed bug in which ensuring an app installed successfully did not work
Save calabash settings to '.calabash_settings' not 'calabash_settings'
Add client_version and server_version methods
Add classes method behaving as the iOS command
Return proper dimensions for webview elements
Add raw AndroidManifest parsing to find launchable activity
Merge branch 'master' into fix/console-rvm-irbrc
Merge branch 'fix/console-rvm-irbrc'
Add ability to specify main_activity with enviroment variable MAIN_ACTIVITY.
Do not invoke methods to find env options if they have been specified in start_test_server_in_background
Fail if unable to uninstall specified app
Look for zipalign in build-tools in not found in tools
scroll_down and scroll_up will only try to scroll the first view by default
Add special scrolling implementation for ListViews