fix execution of git merge-base and remove extraneous newlines

commands.getoutput was producing an error message "'{' is not recognized as an internal or external command," I assume it was trying to run the command in a subshell using sh syntax, which is not valid in a cmd.exe shell.

The whole script should probably be converted to 'subprocess'

Also `if baserev != oldrev:` was failing due to the newline printed after the revision number by the command 'git merge-base'.
IRCContact consume 2 events:

    ('builders', None, 'builds', None, 'new') => A build is started
    ('builders', None, 'builds', None, 'finished') => A build is finished

When we will be able to get the list of changes for a build, the IRCContact must be updated.
Fix sa2ajj's comment
Fix Doc for Dependent Scheduler
Should fix sa2ajj's comment
remove a note about non-working request collapsing

See ticket:2645
Merge pull request #1336 from delanne/DocFix

Fix Doc for Dependent Scheduler
make 5 min tutorial compliant with one-sentence-per-line
update 5 mins tutorial to use plugins
Merge pull request #1310 from socantre/patch-1

fix execution of merge-base and remove extraneous newlines
Merge pull request #1335 from delanne/IRCContact

IRCContact use the DATA API
address @benallard's comment
fix scheduler plugin name (it is schedulers)
Generate the missing indices.
Merge pull request #1339 from benallard/patch-1

Generate the missing indices
The slave property of the slave was renamed conn in 6885d46a3e9
Make AbstractLatentBuildSlave.sendBuilderList similar to BuildSlave.sendBuilderList
Move the disconnect hack to the protocol layer
Merge pull request #1341 from benallard/fix-abstractlatentbuildslave

Fix AbstractLatentBuildslave

Fixes ticket:2970
fix dataspec error reporting

Signed-off-by: Pierre Tardy <pierre.tardy@intel.com>